On large sites the category management screen (/course/index.php?categoryedit=on for 2.4, /course/manage.php in 2.5 ) can quickly become unweildy as the number of categories and sub-categories grows.
Currently you can manage courses on category at a time (/course/category.php?id=5&categoryedit=on for 2.4, /course/manage.php?id=5 for 2.5) but the sub-categories on those pages remain uneditable.
It would be a good, and presumably simple, improvement if the same editing interface that is present for courses on that page, namely a row of icons for editing settings, adding roles, deleting, hiding, moving up and down the list and a tick box for moving elsewhere in the hierarchy, were also available for categories (there's also two icons for backup and restore but those don't apply to categories as far as I'm aware).
The edit category is simply a link, the rest all exist as functionality but are currently located on the main category page.
As well as the usability benefits, this would also allow users assigned at the category level to manage categories and courses within their own category, which is not currently possible with the current site-wide-only interface.