The UI for editing categories is unmanageable once you have more than a handful of categories.
We have hundreds of categories and subcategories and it becomes incredibly awkward to do something simple, like re-arrange the order of two categories or hide a couple of categories in a sub-category.
It would be far better if the category page's "turn editing on" button allowed you to edit the categories in the same way you can edit the courses (e.g. hide, delete, assign roles, up/down arrows, select for group actions).
This would also allow those rights to be decentralised with different users having different access rights, again in the same way as they currently do for courses.