[Coroner]

There are also 2 ways

1.) in the category overview (what I mean is the page where you see all the categories and "maybe" the album below), simply doubleclick beneath the title.
This function is similiar the same as vB and used AJAX.

2.) go into the UserCP oder Administration/Moderation of the UMG, click on "Categories" - right hand you can now create a new category, but .. below that you will see the categorie structure.
Simply click on the category to edit or delete (delete is with edit (see at the bottom))