How to add "Add topic" Button to the forum menu or forum main dashboard
wpForo allows you full customize theme and styles, so you can insert the "Add Topic" button in the category page. However, the topic should be created in some of the existed forums, so you'll need more customizations. In this case, after you click on the "Add topic" button, you'll need to find a way to display the list of the forums (users should select the target forum) for the topic.
I'd suggest you check out wpForo Threaded Layout. In this doc, you can find more about the main features of this forum layout:
We have the same issue.... we got a lot of our users who can't find the Add Topic button because they don't navigate to the actual Forum. (We use the Extended Layour)
We probably get 2 support tickets about it each day. It would be nice to have an Add Topic button from the Main Threaded Layout and if they click it they have to choose the forum to add it to.