I'm glad I can report: This issue is resolved. I was able to find out what was causing this behaviour: A third-party installer script (which was run as root) changed the ownership of several subfolders under ~/.local/share/ to "root", and thus, there was no write access any more.
This had nothing to do with Ubuntu. Thank you all the same, Ulrich -- kmenuedit: unable to create new menu entries https://launchpad.net/bugs/82213 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs