Move topic split instructions to dedicated procedure in "Moderator Instructions"

Previously, the topic split instructions were provided as part of the "Split hijacked topic" procedure.

There are cases other than a hijack where splitting a topic is useful, so it is better to define a general purpose
"Split topic" procedure, then reference that from each of the more specific procedures that require a topic split.

Author: per1234

content/categories/staff/moderation/_topics/moderator-instructions/1.md

@@ -55,6 +55,7 @@ For an overview of the Discourse moderation system, see the "[**Discourse Modera
   - [Make staff post](#make-staff-post)
   - [Adjust user Trust Level](#adjust-user-trust-level)
   - [Silence user](#silence-user)
+  - [Split topic](#split-topic)
   - [Suspend account](#suspend-account)
   - [Change post ownership](#change-post-ownership)
 - [Resources](#resources)
@@ -500,16 +501,7 @@ A topic hijack is when a user makes a reply that is not relevant to the topic. T
 ---
 
 1. Open the hijacked topic.
-1. Click the wrench button ("topic actions") at the bottom of the topic.
-1. From the menu, select "**Select Posts...**".
-   A "**You have selected 0 posts.**" dialog will open.
-1. Click the <kbd>**select**</kbd> button on each post related to the hijack.
-1. Click the <kbd>**move to**</kbd> button.
-   A "**Move to**" dialog will open.
-1. In the "**New Topic Title**" field, enter an appropriate title for the subject of the hijack post.
-1. Select the appropriate [forum category](https://forum.arduino.cc/categories) from the "**Category**" dropdown menu.
-1. Click the <kbd>**Move to New Topic**</kbd> button.
-   The new topic will be created and opened in your browser.
+1. Follow the ["**Split topic**" procedure](#split-topic) to move the posts specific to the hijack to a new topic.
 1. In a reply to the newly created topic, add a ["Staff Post"](#make-staff-post):
    > Please don't hijack topics. I've had to split your post out to its own topic.
    >
@@ -921,6 +913,29 @@ In certain rare cases, the need might arise to silence an account without there
 
 ---
 
+<a name="split-topic"></a>
+
+### [Split topic](#split-topic)
+
+In some cases, it may be useful to move posts to a dedicated topic.
+
+1. Click the wrench button ("topic actions") at the bottom of the topic.
+1. From the menu, select "**Select Posts...**".
+   A "**You have selected 0 posts.**" dialog will open.
+1. Click the **select** button on each post you wish to move to a new topic.
+1. Click the **move to** button.
+   The "**Move to**" dialog will open.
+1. Type an appropriate title for the subject of the new topic in the "**New Topic Title**" field of the "**Move to**" dialog.
+1. Select the appropriate [forum category](https://forum.arduino.cc/categories) from the "**Category**" dropdown menu.
+1. Click the **Move to New Topic** button at the bottom of the dialog.
+   The new topic will be created and opened in your browser.
+1. If the original topic provides potentially useful context to the posts in the new topic, [edit](#edit-post) the first and add a reference to the pre-split topic:
+   ```markdown
+   Continuing the discussion from <!-- TODO: original topic URL -->:
+   ```
+
+---
+
 <a name="suspend-account"></a>
 <a name="suspend-an-account"></a>