I'm aware of the M hotkey, but something I feel is lacking (unless it's already there and I'm missing it), is an overview over what type and how many minions that are under my control.
Quite often during a clash I'll have no idea which minions are still alive, save the M shortcut being grayed out signifying I have none. I find myself retreating them out of a battle just to see what all I have left - or if I have the mana for it, just systematically hitting 5 6 7 and listening for the narrator to tell me I'm already full.
These are slightly awkward workarounds, and I'd really love it if I could just have a simple UI element to show what all I have.