Replace Text Editor system app for different one

I installed Pluma (I want Xed now but not sure about how to install it without getting all X apps, so sticking with Pluma).

it works fine for .txt apps. But for config files, for example if I want to edit a .desktop file, it does not work as expected. I always have to choose “Other Application…”

If I Right-click > Open With … > it only shows GEdit, LibreOffice Writer.

Whatever I do (reset to system defaults, then set PLuma again as default or choose “add to list”), I am unable to get Pluma in that list of “Open With…”.
How to do that?

I also tried renaming it to Text Editor, and naming the old Text Editor to GEdit. Did not help.