Hello

... I can have categories accessible to admins/mods/users, but is there a way to have a category only accessible by certain users while another category might be accessed by another set of users again?

No, not at the moment. To implement this behaviour we need a more complex administration for users and, this would be new, for groups. Ideally an user should be able to be a member of more than one/many group(s).

To implement it is not a five minute task.

Tschö, Auge