Yesterday I mocked up some automatic grouping by the first letter, displayed it using ZO_Tree... and it looked and felt awful. So I scratched that.
In the process I really struggled with the main controls' construction and what the word "panel" means in different contexts, so I started reorganizing that a bit, properly parenting controls where they belong, and also pondering moving some definitions to XML. When I'm done with that I'll try adding a search filter, that seems like a lighter and easier-done-right alternative to categories.