In kubuntu 18.04 the User Manager in Settings can add and delete users, but that’s about it.
I need to modify groups and users so seldomly that I spend more time reading man pages and finding the commands than actually doing the changes!
This answer addresses the question for gnome (if it is still relevant after 10 years or so) but I would prefer a KDE solution. Is there one?
>Solution :
Answering my own question after further digging…
There used to be KUser which did exactly what I was after, but it is no longer maintained.
But the standard repositories contain lxqt-admin-user which does the job instead. To install: sudo apt install --no-install-recommends lxqt-admin. If you don’t use --no-install-recommends it will install several 10s of Mb of stuff instead of a couple of hundred of kb, but still works ok.
Thanks to https://www.kubuntuforums.net/forum/general/documentation/knowledge-base/67127-user-management-2018