In my opinion spells currently take up too much space in your hot keys. By level 3 I already have more spells/abilities/useful items on my hot bar where I have to scroll to a second page. This problem will get worse as you continue to level up.
I think a much more elegant solution would be to have your available spells (prepared spells for casters such as clerics, druids, wizards etc.)/(known spells for casters such as bards, warlocks, etc.) show up when you click the spell slot rectangles above the movement bar. So if you wanted to cast sleep, you'd click Spell Slot I, then click sleep, then target and cast it. For spells upcast at a higher level, for example casting sleep with a level 2 slot, sleep should show under Spell Slot II, perhaps in a separated position above your normal level 2 spells. If you adopted this method a cantrip rectangle should be added as well.
I think this would really clean up the interface and if players wanted to they could still hot key spells they use very regularly and have the rest of them organized just a few clicks away.
In addition, spells and abilities which can only target yourself, for example Mage Armor or Dash, should not require you to click the button and then click yourself/a random spot on the screen. I find this very unintuitive and inconsistent as abilities like hide happen immediately. I've watched streams of new players who struggle using Dash because they click it and nothing seems to happen.
