Not sure why it was deleted but a TL;DR: is:
It can be a hassle to purchase items one by one if an NPC (example atm being ones from mods) has a lot more than just 3 of one item, and it'd be nice if we could have some sort of input to amount when purchasing stuff from merchant NPCs. My finger would greatly appreciate it 😅
I nabbed myself an auto clicking script for AutoHotkey in the meantime 😂