We've been able to replicate the issue on the Moodle 4.3 Sandbox.

The Activity Chooser fails to load when using the create in place option (the ⊕ icon) after indenting course content, and generates a console error.

EDIT: I've attached a simple course backup in case it saves time for Step 2 below.

Expected Behavior

1. Turn editing on in a course
2. In a topic with at least two activities, indent one of them
3. Click the ⊕ icon above the indented content to open Activity Chooser instead of the "Add an activity or resource" link
4. Activity Chooser opens

Actual Behavior

1. Turn editing on in a course
2. In a topic with at least two activities, indent one of them
3. Click the ⊕ icon above the indented content to open Activity Chooser instead of the "Add an activity or resource" link
   • Note: These steps to replicate will fail if you click the "Add an activity or resource link" instead of the ⊕ icon, or if you click the ⊕ icon below the indented content
4. Activity Chooser fails to open
5. Console error (attached) is generated each time you click the ⊕ icon or the "Add an activity or resource" link

We've been able to replicate this issue in Chrome (Version 123.0.6312.87), Firefox (Version 124.0.1), and Safari (Version 17.4.1). This is occurring in Moodle 4.3.3.

A screencast of the issue, screenshot of the console log, and a copy of the console error log from Chrome is available in this Google Drive folder.

The cause of the problem is, that the ⊕ button uses the "num" attribute of the section. When get_fragment is used, the cmitem is rendered without a section so there is no "num" attribute.