gedit 2.28.4, on
When I click on
Edit > Preferences, I can't modify anything, as everything is grayed out.
Also, I could not re-size the preferences window to locate the 'Edit' button as suggested on other forums.
It turns out the
gedit configuration files were missing completely. Reinstalling fixed the problem.
As far as i know the gedit preferences stored in /usr/share/gedit and in other root-owned places such a gtksourceview. you should change permission or simple try run gedit under root, to do all needed changes.