Hotkey Request: Target Champions Only + Player Attack Only Click
It's awkward not to have this on one key. The reason to use this is so that you don't accidentally move when you're trying to target a player. For example, let's say you have just "Target Champions Only" pressed and try to click a Yasuo but he dashes past where you're clicking. Without "Player Attack Only Click", you simply move to where you clicked.
It's an annoying and pointless mechanical error that feels more random than skillful. It's just something needlessly frustrating. Having to hold both buttons is a hassle and I think it's not too much to have this as a single key option. I don't think anyone uses "Player Attack Only Click" outside of this sort of specific scenario anyway (when you want no movement command issued by accident). If you're trying to avoid accidental movements while farming, you'll be using attack move and not this.
summary of how this is different from just target champions only:
basically, you issue an auto attack command in addition to just targeting champions. no movement occurs if you do not click on a champion.
with target champs only, maybe you just want to use it for a point and click spell etc., well this would make you automatically auto the targeted champion (wouldn't be able to use point and click spells). the purpose is quite different.