[Sam Bauers]

The sub-forum setup may not be what you are after exactly, but it is the only way to closely approximate your needs using a default install.

Categories (similar to what you show in your image) was something I spent quite a lot of effort on a few releases ago. It never made it to core, but there is still an intention to add similar functionality in the future. I’m thinking maybe we should have forums which don’t hold topics, and act as de-facto categories when they contain sub-forums. This is future stuff though, for now sub-forums is as good as it gets.