Sorry I had forgotten to add the filter to show only the user’s own Chapter posts in that field, which is what was intended. It should now only show your own Chapters. Please confirm by updating the post. Regarding that, I’m at work at the moment but I’ll be enabling comments on Bug Report posts later to make a back and forth conversation easier, and the Staff Notes will be used only for updates on the progress of resolving the issue.

Resolved. NOTE: In cases where it is necessary to show all posts (e.g. when adding content to a Collection), the Edit button when hovering over posts in the selection field has temporarily been removed for all users. The plugin dev will add an option to only show the edit button on posts that the user is the author of. But until then, it's removed for everyone, and posts should be edited using the Edit button on their single pages.