The current method of using consumables is cumbersome to say the least. On top of this, some items like potions have a re-use timer and you can't see this timer- all you can do is keep trying to use the item again until it works.

Being able to place your mot commonly used consumables on the action bar would alleviate this annoyance and would also allow for the possibility of seeing the cooldown time.

I have so many potions and other consumables and I rarely use them only because it's hard to access them quickly- if you take too long to use them, often their benefit can be negated.