Nested / hierarchical categories
Good UI design rules include the idea that a person can grasp about 7 short words or menu items in a glance.
My category list is getting quite large, and some of the categories contain more items than I can view without scrolling.
Many of my categories are related to one another such that a two level or multi-level category hierarchy could easily be made with logical relationships.
This would allow me to make more categories also with fewer items.