As I said, you alot of forum software that has pagination for the categories/forums.
This is why the time has not been spent adding this into bbPress, most of the time it is not needed.
What you should do is organize more “top level” categories if that’s what it takes.
category A
- sub-category A1
– forum AA1
– forum AA2
category B
– sub-category B1
– forum BB1
– forum BB2