I am not sure how to explain this...

When we have a category on forum index with, lets say, 5 forums.
Then we cant set this category to show subforums. We dont have this option with categories.

But if we change the category to a forum and then enable display of subforums, and after that we turn the forum back to being a category then we have a category with, well not subforums, forums displayed.
And by that I mean the direct link to the forum.

And that was really what I wanted, but its easier if that option is enabled in categories.