collapsing categories list in the admin (not on site)

just spent an hour or so looking through the plug-in listings, but i don’t think i found exactly what i was looking for, so i figured i’d ask the community ??

a site that i am building will have lots of categories and sub categories (and sub subs). i was just looking for a way to not make that so confusing for the person i am building it for. instead of having one really long, scrolling list in the admin, is there a plugin that would make the lists collapsible? so that only the main cats would appear at first, with the little plus box next to them to drill down further?

this is only something they’d need in the dashboard, not something needed on the site