Been suggesting this since ARR. Macros could do the trick, too, ofc, if only the devs hadn't intentionally gutted them from the start, but I'd honestly prefer this. Alternatively, we should at least be able to use stacked keys (e.g. Cure II and Glare on the same hotbar slot, swapping upon ally/enemy target) and specific targeting procedures bindable to any skill, including those in stacked keys.