I think it'd be a great QoL addition if, while hovering your mouse over the different sections of your hotbar, you could scroll it to see all of your items, spells, and so on. So you wouldn't have to filter by specific categories or move the separator every time you want to search for an item or spell to use.

Ideally you should be able to scroll individual categories, so for example if I scroll through the items separator, only the items separator would be scrolled, and not my whole hotbar.

[Linked Image from i.imgur.com]