The currently installed version JSON Editor (2.15.0) in the Patternkit module is several releases behind the latest version (2.15.2) and does not include a variety of improvements and bug fixes.
The installed version of the library should be updated to version 2.15.2 (or later if a new release comes out). Existing functionality should then be regression tested to ensure no breakage.
One example issue, specifically, is the one reported here where values for select dropdowns are not being pre-filled.
None
None
None
Active
9.1
Schema Editor
Attached is a rerolled patch for 9.1.1 without the unnecessary composer change that causing a conflict.
My above rerolled patch for 9.1.1 is invalid. I've re-uploaded a working version.
Can confirm, this patch worked and resolved the issue.