Request: Add a shortcut for FDS disk-side switching or an option to auto switch disk sides (please read before replying)

Before replying please read the explanation for this request.

I know that on a PC, or any regular controller with 4 buttons or more, it's easy to assign the swap disk sides to a couple of unused keys. But the purpose of this request is because Nestopia also works with the NES Classic through Retroarch, and the original NES controller only has 2 buttons. Assigning the disk side change option to the A/B/Start/Select buttons cause problems because if you press any of those buttons during gameplay, it will unwillingly change or eject the disk, and that will cause many games to error-out when trying to load a new segment that's supposed to be on the disk-side you were using. This is specially true for RPGs that are constantly reading from the disk when entering battle scenes or houses.

This wouldn't a problem if Retroarch allowed for user-set double binds or button combinations, but it doesn't. It has a few pre-set button combinations that are being used for other things, but a user cannot set their own. So the only option left is for Nestopia to have a button combination of its own (Down+Start / Up+ Start should work fine to swap disk sides) or to have an option to auto swap sides like how the native NES Classic emulator does for FDS games.

is this an option that can be added for NES Classic users using the original 2-button controller?

Start by reviewing Nestopia's existing FDS disk-side switching controls and the Retroarch NES Classic controller constraints described in the issue. Determine whether a button combination, automatic side switching, or both is feasible, then verify the chosen behavior does not trigger during normal two-button gameplay and works when games load another disk side.