Can use any item (not just heal potions) at a given hp % in heals.
I have a feign death potion there, works fine. The potion is also on my potions belt.
Any item in the potion belt stays in your bags btw you can setup a hotkey for it, probably so you can change potions easier, the hotkey you setup will refer to that belt slot not the item. But givenow you can just drag the potion itself to a hotbar don't see it getting much use.