Autoconfig game and core specific overides

I chose RetroArch over MAME because of it’s intuitive controller setups but I since bought an arcade style controller with an Xbox layout. it’s great on every core except Arcade (I have a lot of arcade games) and Sega Genesis/Mega Drive ones. I spent forever going over the settings before I realized that there wasn’t any way reassign the buttons for it without messing them up when I want to switch to a more traditional controller. Can someone please add this feature I’m sure I’m not the only one who runs into this problem.