I’ve seen this asked for in the General forum, but I haven’t seen that it’s already been done. I’m sorry if I missed it.
Stella, as a stand-alone piece of software, supports Atari paddles. I can’t find such support in RetroArch. This would be an excellent edition. Super Breakout, Kaboom, Warlords. These are good games that are playable in Stella but not in RetroArch.
Again, maybe I missed the paddle option, or I just haven’t done a good job adjusting my config.