Is it possible to createa Plugin that allows Usergroups to edit Member's Additional Group and Display Group via ModCP?
There are no available plugins to do this, sorry.
This is a plugin requests section.
Could be possible, yes. But why would a moderator do such a thing?
Because I need him/her to.
If you need it then you need it.
But, doesn't the group leaders feature works for you?
I can't just assign Mods for every group. Besides, I need the ability for Mods to change display group as well.