I'm currently working with SMF 2.0.2.
When creating or editing Membergroups, we can (by default) choose which Forum Boards will be visible to the Membergroup. All available Forum Boards (and their child boards) are listed with check-boxes beside them.
If we have a large number of boards active in several Forum Board Groups (categories), the list of active boards gets quite long. for example, my project currently has 8 Board Groups (categories) including the "General Category" containing the "General Discussions" Board. One of my Board Groups (categories) has 340 Forum Boards (plus child boards for each) in it. So... as you can see... the list of available boards I need to check off for Visibility settings is very long.
Refinement Suggestion - for the Boards the membergroup can see list:
1) List the available Boards by Board Group (category), with boards (and child boards) appropriately indented.
2) Board Group (category) titles would be bold, and maybe colored, so as to stand out prominently.
3) Each Board Group (category) title's Boards list would be collapsed be default, and expandable.
3) A tick-box beside Each Board Group (category) title would make the whole Group (and all boards in it) visible at once.
4) If only one of 340 boards in a Board Group is to be visible, the Board Group title and board title would be checked.