Thanks, I think I understand better now.
If I have a forum with categories that correspond to groups something like:
- low
- medium low
- medium
- medium high
- high
In the current scheme it is easily possible to restrict access to the higher categories from each of the lower groups until certain criteria is met. But higher groups always have access to lower categories.
What you are wanting is a way to not allow higher groups access to lower categories.
In other words, as a contrived example, if a lower group was “associates” and a higher group was “doctorate”, the AS would be lost in PHD topics so should not have access, and the PHD would have no interest in AS topics.
AFAIK, the closest thing to this would be to Mute the AS category from the PHD group. However, the Mute feature is not about permissions, it could help reduce the “noise” of the muted categories, but it would not prevent access to them.