Changes made to application menu entries are not respected by Kickoff, KRunner etc

I’m facing a slightly weird issue and I don’t know how to troubleshoot any further at the moment.

Basically, I can edit menu entries with KMenuEdit just fine (e. g. adding environment variables to the Steam shortcut), and when I click save, a .desktop entry with my changes is written to ~/.local/share/applications, as expected and without any error messages.
However, these changes are not respected when I launch the respective application from KRunner or Kickoff, nor are they displayed when launching KMenuEdit again. Apparently, they still use the system-wide .desktop file rather than my local override.

Custom local menu entries that don’t override anything else work as expected.

This issue is not present on a fresh user account, indicating that this is some kind of configuration issue with my user account.
Note that I’m still on Plasma 5.27.10, on Fedora 39.

Does someone have any idea what could be causing this?