[Mobile] How can I add new message on last by manually

Dear Developers,

Thank you very much for your support and I am sorry I don't know how to add a new message at end of the data with attributes manually.

Could you please kindly tell me, how can I add a new message by inserting it at end of the document with the attribute manually?

Thank you very much

[MagTuxGit]

delta.insert('a new message', {'bold': true});

Thank you very much @MagTuxGit .
But when I use quillController.document.toDelta().insert('(edited)', {'color' : '#888888'});, it doesn't add that message.
Could you please kindly help me 🙏
Thank you very much

I would like to show (edited) at end of message.

When I use the following code, it can show (edited) at end of message but last message ending with header 1, "(edited)" is also showing header attribute

      quillController!.document.insert(quillController!.document.length - 1,
          ' ${AppLocalizations.of(context)!.message_edited}');
      quillController!.document.format(quillController!.document.length - (edited.length),
          edited.length, ColorAttribute('#888888'));
      quillController!.document.format(
          quillController!.document.length - (edited.length), edited.length, SmallAttribute());

before adding "(edited)", log output:

[{"insert":"Test","attributes":{"background":"#004d40"}},{"insert":" "},{"insert":"22","attributes":{"code":true}},{"insert":"\n","attributes":{"header":1}}]

After adding "(edited)", log output

[{"insert":"Test","attributes":{"background":"#004d40"}},{"in
sert":" "},{"insert":"22 ","attributes":{"code":true}},{"insert":"(edited)","attributes":{"code":true,"color":"#888888","small":true}},{"insert":"\n","attributes":{"header":1}}]