Namely the ability to filter out cases/keys that do not have a matching key/case respectively. For example,. you click the button, all the keys that don't have fitting cases disappear from sight, and the same happens to cases with keys. So say you have 4 splatter cases, and a tech key, but no splatter keys or tech cases. You click "Filter out mismatch" or whatever it would be called, and poof, gone. Would help greatly with organization.
The ability to sort alphabetically would also help, rather than by item type. Just more sorting features in general. For example being able to push mis-matching keys/cases to the bottom instead of completely removing them.
I'd also like to be able to trade 2-3 cases for another, random case, excluding the category of cases you just put in.