This add-on allows users to hide or show "optional forums". The forums to be made optional are selected by the admin.
If a user chooses to hide an optional forum, he won't see it in forum lists, or in New Posts.
It effectively allows limited admin delegation of node viewing rights to users themselves.
This can be useful for boards where some of the sub-forums are controversial or NSFW. Users are no longer faced with the choice of: not viewing the board at all, or viewing a board they partly dislike the content of. They can simply "opt out" of the sub-forums they don't like.
After installing the add-on, set who has permissions to set optional forums.
In admin, go to the settings of the forum you want to make optional (Applications -> Node Tree -> Display Node Tree -> [choose forum] -> Forum Options)
Select Make Forum Optional
Set the default. If show by default is chosen, users can elect to hide the forum. If hide by default is chosen, the forum is hidden to all users until they elect to show it.
Users click Optional Forums in their control panel to access the list, and select the forums they want to show or hide.