Easiest way to reset custom hotkey binds in retroarch

[brimby]

3B+
4.5.1
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I built a Retropie for my friend (based on the official image) and did a lot of work in the UI with my controller, which is an actual SNES controller (through a USB converter.) But before I mailed it off to him I made sure to delete es_input.cfg and deleted the controller config file out of /configs/all/retroarch/autoconfig so I thought it would be all clean for him to start fresh with the controller he bought, which is a basic Amazon USB retro controller. Well, it turned out it wasn't all fresh, because none of his hotkeys worked, and he got stuck in-game.

I think the problem is that I set some custom hotkey binds in retroarch, and they are expecting the button "numbers" that came from my controller. I think his buttons give off different number signals than mine, if that makes sense. Like maybe my A button registers as button "2" but his registers as button "3" since it's a different controller. I'm overstating myself, but basically my question is, is there a way to reset these keybinds in retroarch that doesn't involve editing the actual retroarch.cfg file? My friend isn't super technical so I'd prefer to give him easier instructions than all that if possible. Thanks!