diff --git a/src/authz-module/data/api.ts b/src/authz-module/data/api.ts
index 2ff3724..1821956 100644
--- a/src/authz-module/data/api.ts
+++ b/src/authz-module/data/api.ts
@@ -40,7 +40,7 @@ export type PermissionsByRole = {
   userCount: number;
 };
 export interface PutAssignTeamMembersRoleResponse {
-  completed: { user: string; status: string }[];
+  completed: { userIdentifier: string; status: string }[];
   errors: { userIdentifier: string; error: string }[];
 }
 
diff --git a/src/authz-module/libraries-manager/ToastManagerContext.test.tsx b/src/authz-module/libraries-manager/ToastManagerContext.test.tsx
index fe67c41..23bfc9a 100644
--- a/src/authz-module/libraries-manager/ToastManagerContext.test.tsx
+++ b/src/authz-module/libraries-manager/ToastManagerContext.test.tsx
@@ -137,4 +137,80 @@ describe('ToastManagerContext', () => {
     expect(logError).toHaveBeenCalled();
     expect(retryFn).toHaveBeenCalled();
   });
+
+  it('respects custom delay when provided', async () => {
+    const user = userEvent.setup();
+
+    const DelayTestComponent = () => {
+      const { showToast } = useToastManager();
+
+      const handleShowToastWithDelay = () => showToast({
+        message: 'Custom delay toast',
+        type: 'success',
+        delay: 1000, // Custom 1 second delay
+      });
+
+      return (
+        <button type="button" onClick={handleShowToastWithDelay}>Show Toast With Custom Delay</button>
+      );
+    };
+
+    renderWrapper(
+      <ToastManagerProvider>
+        <DelayTestComponent />
+      </ToastManagerProvider>,
+    );
+
+    const showButton = screen.getByText('Show Toast With Custom Delay');
+    await user.click(showButton);
+
+    await waitFor(() => {
+      expect(screen.getByText('Custom delay toast')).toBeInTheDocument();
+    });
+
+    await waitFor(() => {
+      expect(screen.getByText('Custom delay toast')).toBeInTheDocument();
+    }, { timeout: 600 });
+
+    // Toast should disappear after the custom delay (1000ms)
+    await waitFor(() => {
+      expect(screen.queryByText('Custom delay toast')).not.toBeInTheDocument();
+    }, { timeout: 1200 });
+  });
+
+  it('uses default delay when delay prop is not provided', async () => {
+    const user = userEvent.setup();
+
+    const DefaultDelayTestComponent = () => {
+      const { showToast } = useToastManager();
+
+      const handleShowToastWithoutDelay = () => showToast({
+        message: 'Default delay toast',
+        type: 'success',
+      // No delay prop provided
+      });
+
+      return (
+        <button type="button" onClick={handleShowToastWithoutDelay}>Show Toast With Default Delay</button>
+      );
+    };
+
+    renderWrapper(
+      <ToastManagerProvider>
+        <DefaultDelayTestComponent />
+      </ToastManagerProvider>,
+    );
+
+    const showButton = screen.getByText('Show Toast With Default Delay');
+    await user.click(showButton);
+
+    await waitFor(() => {
+      expect(screen.getByText('Default delay toast')).toBeInTheDocument();
+    });
+
+    // DEFAULT_TOAST_DELAY is 5000ms
+    await waitFor(() => {
+      expect(screen.queryByText('Default delay toast')).not.toBeInTheDocument();
+    }, { timeout: 5050 });
+  }, 5100);
 });
diff --git a/src/authz-module/libraries-manager/ToastManagerContext.tsx b/src/authz-module/libraries-manager/ToastManagerContext.tsx
index 12089f4..7f0d9b1 100644
--- a/src/authz-module/libraries-manager/ToastManagerContext.tsx
+++ b/src/authz-module/libraries-manager/ToastManagerContext.tsx
@@ -5,6 +5,7 @@ import { logError } from '@edx/frontend-platform/logging';
 import { useIntl } from '@edx/frontend-platform/i18n';
 import { Toast } from '@openedx/paragon';
 import messages from './messages';
+import { DEFAULT_TOAST_DELAY } from './constants';
 
 type ToastType = 'success' | 'error' | 'error-retry';
 
@@ -19,11 +20,12 @@ export const ERROR_TOAST_MAP: Record<number | string, { type: ToastType; message
   DEFAULT: { type: 'error-retry', messageId: 'library.authz.team.toast.default.error.message' },
 };
 
-interface AppToast {
+export interface AppToast {
   id: string;
   message: string;
   type: ToastType;
   onRetry?: () => void;
+  delay?: number;
 }
 
 const Bold = (chunk: string) => <b>{chunk}</b>;
@@ -47,7 +49,7 @@ export const ToastManagerProvider = ({ children }: ToastManagerProviderProps) =>
   const [toasts, setToasts] = useState<(AppToast & { visible: boolean })[]>([]);
 
   const showToast = (toast: Omit<AppToast, 'id'>) => {
-    const id = `toast-notification-${Date.now()}`;
+    const id = `toast-notification-${Date.now()}-${Math.floor(Math.random() * 1000000)}`;
     const newToast = { ...toast, id, visible: true };
     setToasts(prev => [...prev, newToast]);
   };
@@ -92,6 +94,7 @@ export const ToastManagerProvider = ({ children }: ToastManagerProviderProps) =>
             key={toast.id}
             show={toast.visible}
             onClose={() => discardToast(toast.id)}
+            delay={toast.delay ?? DEFAULT_TOAST_DELAY}
             action={toast.onRetry ? {
               onClick: () => {
                 discardToast(toast.id);
diff --git a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.test.tsx b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.test.tsx
index 0939eb4..5ddb309 100644
--- a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.test.tsx
+++ b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.test.tsx
@@ -21,20 +21,23 @@ jest.mock('./AddNewTeamMemberModal', () => {
     isOpen, close, onSave, isLoading, formValues, handleChangeForm,
   }) => (
     isOpen ? (
-      <div data-testid="add-team-member-modal">
-        <button type="button" onClick={close} data-testid="close-modal">Close</button>
-        <button type="button" onClick={onSave} data-testid="save-modal">Save</button>
+      <div data-testid="add-team-member-modal" role="dialog" aria-label="Add New Team Member">
+        <button type="button" onClick={close} aria-label="Close modal" data-testid="close-modal">Close</button>
+        <button type="button" onClick={onSave} aria-label="Save team member" data-testid="save-modal">Save</button>
         <textarea
           name="users"
           value={formValues?.users || ''}
           onChange={handleChangeForm}
           data-testid="users-input"
+          aria-label="Enter user emails or usernames"
+          placeholder="Enter emails or usernames"
         />
         <select
           name="role"
           value={formValues?.role || ''}
           onChange={handleChangeForm}
           data-testid="role-select"
+          aria-label="Select role"
         >
           <option value="">Select role</option>
           <option value="admin">Admin</option>
@@ -146,7 +149,7 @@ describe('AddNewTeamMemberTrigger', () => {
       expect(screen.queryByTestId('add-team-member-modal')).not.toBeInTheDocument();
     });
 
-    expect(screen.getByText('2 team members added successfully.')).toBeInTheDocument();
+    expect(screen.getByText(/2 team members added successfully/)).toBeInTheDocument();
   });
 
   it('displays mixed success and error toast on partial success', async () => {
@@ -179,6 +182,50 @@ describe('AddNewTeamMemberTrigger', () => {
     expect(screen.getByTestId('add-team-member-modal')).toBeInTheDocument();
   });
 
+  it('filters out successfully added users from error users list', async () => {
+    const user = userEvent.setup();
+
+    const mockPartialResponse = {
+      completed: [
+        { userIdentifier: 'alice@example.com' },
+      ],
+      errors: [
+        { userIdentifier: 'bob@example.com', error: 'USER_NOT_FOUND' },
+        { userIdentifier: 'charlie@example.com', error: 'USER_NOT_FOUND' },
+      ],
+    };
+
+    (useAssignTeamMembersRole as jest.Mock).mockReturnValue({
+      mutate: jest.fn((_variables, { onSuccess }) => {
+        onSuccess(mockPartialResponse);
+      }),
+      isPending: false,
+    });
+
+    renderWrapper(<ToastManagerProvider><AddNewTeamMemberTrigger libraryId={mockLibraryId} /></ToastManagerProvider>);
+
+    const triggerButton = screen.getByRole('button', { name: /add new team member/i });
+    await user.click(triggerButton);
+
+    const usersInput = screen.getByRole('textbox', { name: /Enter user emails or usernames/i });
+    const roleSelect = screen.getByRole('combobox', { name: /Select role/i });
+    const saveButton = screen.getByRole('button', { name: 'Save team member' });
+
+    await user.type(usersInput, 'alice@example.com, bob@example.com, charlie@example.com');
+    await user.selectOptions(roleSelect, 'editor');
+    await user.click(saveButton);
+
+    await waitFor(() => {
+      expect(usersInput).toHaveValue('bob@example.com, charlie@example.com');
+    });
+
+    await user.type(usersInput, ', new@example.com');
+
+    await waitFor(() => {
+      expect(usersInput).toHaveValue('bob@example.com, charlie@example.com, new@example.com');
+    });
+  });
+
   it('displays only error toast when all additions fail', async () => {
     const user = userEvent.setup();
     renderWrapper(<ToastManagerProvider><AddNewTeamMemberTrigger libraryId={mockLibraryId} /></ToastManagerProvider>);
@@ -207,6 +254,33 @@ describe('AddNewTeamMemberTrigger', () => {
     expect(screen.getByTestId('add-team-member-modal')).toBeInTheDocument();
   });
 
+  it('displays different error toast when different errors happen', async () => {
+    const user = userEvent.setup();
+    renderWrapper(<ToastManagerProvider><AddNewTeamMemberTrigger libraryId={mockLibraryId} /></ToastManagerProvider>);
+
+    const triggerButton = screen.getByRole('button', { name: /add new team member/i });
+    await user.click(triggerButton);
+
+    const saveButton = screen.getByRole('button', { name: 'Save team member' });
+    await user.click(saveButton);
+
+    const [, { onSuccess }] = mockMutate.mock.calls[0];
+    onSuccess({
+      completed: [],
+      errors: [
+        { userIdentifier: 'unknown@example.com', error: 'user_not_found' },
+        { userIdentifier: 'already@example.com', error: 'user_already_has_role' },
+      ],
+    });
+
+    await waitFor(() => {
+      expect(screen.getByText(/We couldn't find a user for 1 email address or username/)).toBeInTheDocument();
+      expect(screen.getByText(/The user already has the role/)).toBeInTheDocument();
+    });
+
+    expect(screen.getByRole('dialog', { name: 'Add New Team Member' })).toBeInTheDocument();
+  });
+
   it('resets form values after successful addition with no errors', async () => {
     const user = userEvent.setup();
     renderWrapper(<ToastManagerProvider><AddNewTeamMemberTrigger libraryId={mockLibraryId} /></ToastManagerProvider>);
@@ -258,7 +332,7 @@ describe('AddNewTeamMemberTrigger', () => {
 
     // Toast should be visible
     await waitFor(() => {
-      expect(screen.getByText('1 team member added successfully.')).toBeInTheDocument();
+      expect(screen.getByText(/1 team member added successfully/)).toBeInTheDocument();
     });
 
     // Find and close the toast
diff --git a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.tsx b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.tsx
index f58d691..981cc07 100644
--- a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.tsx
+++ b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/AddNewTeamMemberTrigger.tsx
@@ -6,10 +6,12 @@ import { Plus } from '@openedx/paragon/icons';
 import { PutAssignTeamMembersRoleResponse } from 'authz-module/data/api';
 import { useAssignTeamMembersRole } from '@src/authz-module/data/hooks';
 import { RoleOperationErrorStatus } from '@src/authz-module/constants';
-import { useToastManager } from '@src/authz-module/libraries-manager/ToastManagerContext';
+import { AppToast, useToastManager } from '@src/authz-module/libraries-manager/ToastManagerContext';
+import { DEFAULT_TOAST_DELAY } from '@src/authz-module/libraries-manager/constants';
 import AddNewTeamMemberModal from './AddNewTeamMemberModal';
 import messages from './messages';
 
+type AppToastOmitIdType = Omit<AppToast, 'id'>;
 interface AddNewTeamMemberTriggerProps {
   libraryId: string;
 }
@@ -58,53 +60,72 @@ const AddNewTeamMemberTrigger: FC<AddNewTeamMemberTriggerProps> = ({ libraryId }
     setFormValues((prev) => ({ ...prev, [name]: value }));
   };
 
-  const handleErrors = (
+  const buildErrorMessages = (
     errors: PutAssignTeamMembersRoleResponse['errors'],
-    successfulCount: number,
-  ) => {
+  ): Array<AppToastOmitIdType> => {
     const notFoundUsers = errors
       .filter((err) => err.error === RoleOperationErrorStatus.USER_NOT_FOUND)
       .map((err) => err.userIdentifier.trim());
 
-    const alreadyHasRole = errors.some(
-      (err) => err.error === RoleOperationErrorStatus.USER_ALREADY_HAS_ROLE,
+    const otherErrors = errors.filter(
+      (err) => err.error !== RoleOperationErrorStatus.USER_NOT_FOUND
+       && err.error !== RoleOperationErrorStatus.USER_ALREADY_HAS_ROLE,
     );
 
-    if (alreadyHasRole && errors.length === 1 && !successfulCount) {
-      showToast({
-        message: intl.formatMessage(messages['libraries.authz.manage.assign.role.existing']),
-        type: 'error',
-      });
-      handleClose();
-      return;
-    }
-
-    if (notFoundUsers.length) {
-      setErrorUsers(notFoundUsers);
-      setIsError(true);
-      setFormValues((prev) => ({
-        ...prev,
-        users: notFoundUsers.join(', '),
-      }));
-
-      const toastMessage = successfulCount
-        ? intl.formatMessage(messages['libraries.authz.manage.add.member.partial'], {
-          countSuccess: successfulCount,
-          countFailure: notFoundUsers.length,
-          Bold,
-          Br,
-        })
-        : intl.formatMessage(messages['libraries.authz.manage.add.member.failure'], {
-          count: notFoundUsers.length,
-          Bold,
-          Br,
-        });
-
-      showToast({
-        message: toastMessage,
-        type: 'error',
+    const result: Array<AppToastOmitIdType> = [];
+
+    const errorTypes = [
+      {
+        errorMessageId: 'libraries.authz.manage.add.member.failure.not.found',
+        users: notFoundUsers,
+      },
+      {
+        errorMessageId: 'libraries.authz.manage.add.member.failure.generic',
+        users: otherErrors,
+      },
+    ];
+
+    errorTypes.forEach(({ errorMessageId, users }) => {
+      if (users.length === 0) { return; }
+      const errorMessage = intl.formatMessage(messages[errorMessageId], {
+        count: users.length,
+        userIds: users.join(', '),
+        Bold,
+        Br,
       });
-    }
+      result.push({ message: errorMessage, type: 'error' });
+    });
+
+    return result;
+  };
+
+  const buildSuccessMessage = (completed: PutAssignTeamMembersRoleResponse['completed']): AppToastOmitIdType => {
+    const userIds = completed.map((user) => user.userIdentifier).join(', ');
+    const successMessage = intl.formatMessage(messages['libraries.authz.manage.add.member.success'], {
+      count: completed.length,
+      userIds,
+    });
+
+    return {
+      message: successMessage,
+      type: 'success',
+    };
+  };
+
+  const buildRoleAlreadyAssignedMessage = (
+    roleAlreadyAsignedUsers: PutAssignTeamMembersRoleResponse['errors'],
+  ): AppToastOmitIdType => {
+    const roleAlreadyAssignedUserIds = roleAlreadyAsignedUsers.map((err) => err.userIdentifier.trim());
+    const roleAlreadyAssignedMessage = intl.formatMessage(messages['libraries.authz.manage.assign.role.existing'], {
+      count: roleAlreadyAssignedUserIds.length,
+      userIds: roleAlreadyAssignedUserIds.join(', '),
+      Bold,
+      Br,
+    });
+    return {
+      message: roleAlreadyAssignedMessage,
+      type: 'success',
+    };
   };
 
   const handleAddTeamMember = () => {
@@ -125,20 +146,44 @@ const AddNewTeamMemberTrigger: FC<AddNewTeamMemberTriggerProps> = ({ libraryId }
       assignTeamMembersRole(variables, {
         onSuccess: (response) => {
           const { completed, errors } = response;
-
-          if (completed.length && !errors.length) {
-            showToast({
-              message: intl.formatMessage(messages['libraries.authz.manage.add.member.success'], {
-                count: completed.length,
-              }),
-              type: 'success',
-            });
-            handleClose();
-            return;
+          const feedbackMessages: Array<AppToastOmitIdType> = [];
+          const { USER_ALREADY_HAS_ROLE } = RoleOperationErrorStatus;
+          // Users who already have the role assigned are not considered errors
+          const roleAlreadyAssignedUsers = errors.filter((error) => error.error === USER_ALREADY_HAS_ROLE);
+          const cleanErrors = errors.filter((error) => error.error !== USER_ALREADY_HAS_ROLE);
+
+          if (completed.length) {
+            feedbackMessages.push(buildSuccessMessage(completed));
+          }
+          if (roleAlreadyAssignedUsers.length) {
+            feedbackMessages.push(buildRoleAlreadyAssignedMessage(roleAlreadyAssignedUsers));
+          }
+          if (cleanErrors.length) {
+            const errorMessages = buildErrorMessages(cleanErrors);
+            feedbackMessages.push(...errorMessages);
+
+            const successUserIds = [
+              ...completed.map(c => c.userIdentifier),
+              ...roleAlreadyAssignedUsers.map(r => r.userIdentifier),
+            ];
+
+            const errorUserIds = normalizedUsers.filter((user) => !successUserIds.includes(user));
+            setErrorUsers(errorUserIds);
+            setIsError(true);
+            setFormValues((prev) => ({
+              ...prev,
+              users: errorUserIds.join(', '),
+            }));
           }
 
-          if (errors.length) {
-            handleErrors(errors, completed.length);
+          // Calculate delay based on the number of feedback messages, 5 seconds per message
+          const delay = DEFAULT_TOAST_DELAY * feedbackMessages.length;
+          feedbackMessages.forEach(({ message, type }) => {
+            showToast({ message, type, delay });
+          });
+
+          if (!cleanErrors.length) {
+            handleClose();
           }
         },
         onError: (error, retryVariables) => {
diff --git a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/messages.ts b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/messages.ts
index c9daa33..05e28d5 100644
--- a/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/messages.ts
+++ b/src/authz-module/libraries-manager/components/AddNewTeamMemberModal/messages.ts
@@ -53,22 +53,22 @@ const messages = defineMessages({
   },
   'libraries.authz.manage.add.member.success': {
     id: 'libraries.authz.manage.add.member.success',
-    defaultMessage: '{count, plural, one {# team member added successfully.} other {# team members added successfully.}}',
+    defaultMessage: '{count, plural, one {# team member added successfully} other {# team members added successfully}} ({userIds})',
     description: 'Success message when adding new team members',
   },
-  'libraries.authz.manage.add.member.failure': {
-    id: 'libraries.authz.manage.add.member.failure',
-    defaultMessage: '<Bold>We couldn\'t find a user for {count, plural, one {# email address or username.} other {# email addresses or usernames.}}</Bold><Br></Br> Please check the values and try again, or invite them to join your organization first.',
-    description: 'Error message when adding new team members',
+  'libraries.authz.manage.add.member.failure.not.found': {
+    id: 'libraries.authz.manage.add.member.failure.not.found',
+    defaultMessage: '<Bold>We couldn\'t find a user for {count, plural, one {# email address or username} other {# email addresses or usernames}}.</Bold><Br></Br> Please check the values ({userIds}) and try again, or invite them to join your organization first.',
+    description: 'Error message in case of user not found when adding new team members',
   },
-  'libraries.authz.manage.add.member.partial': {
-    id: 'libraries.authz.manage.add.member.failure',
-    defaultMessage: '<Bold>{countSuccess, plural, one {# team member added successfully.} other {# team members added successfully.}}. We couldn\'t find a user for {countFailure, plural, one {# email address or username.} other {# email addresses or usernames.}}</Bold><Br></Br> Please check the values and try again, or invite them to join your organization first.',
-    description: 'Error message when adding new team members',
+  'libraries.authz.manage.add.member.failure.generic': {
+    id: 'libraries.authz.manage.add.member.failure.generic',
+    defaultMessage: '<Bold>We couldn\'t assign the role to {count, plural, one {team member} other {team members}} ({userIds})}.</Bold><Br></Br> Please check the values and try again.',
+    description: 'Generic error message when adding new team members',
   },
   'libraries.authz.manage.assign.role.existing': {
     id: 'libraries.authz.manage.assign.existing',
-    defaultMessage: 'The user already has the role.',
+    defaultMessage: 'The {count, plural, one {user already has} other {users already have}} the role ({userIds}).',
     description: 'Libraries AuthZ assign existing role',
   },
   'libraries.authz.manage.tooltip.roles.extra.info': {
diff --git a/src/authz-module/libraries-manager/constants.ts b/src/authz-module/libraries-manager/constants.ts
index 27446a1..e57f138 100644
--- a/src/authz-module/libraries-manager/constants.ts
+++ b/src/authz-module/libraries-manager/constants.ts
@@ -49,3 +49,5 @@ export const libraryPermissions: PermissionMetadata[] = [
   { key: CONTENT_LIBRARY_PERMISSIONS.MANAGE_LIBRARY_TEAM, resource: 'library_team', description: 'View the list of users who have access to the library.' },
   { key: CONTENT_LIBRARY_PERMISSIONS.VIEW_LIBRARY_TEAM, resource: 'library_team', description: 'Add, remove, and assign roles to users within the library.' },
 ];
+
+export const DEFAULT_TOAST_DELAY = 5000;