As on this post, hk+button gor special commands like save or load state should be working on mupen. https://github.com/recalbox/recalbox-os/issues/616 The only combination working for me is to exit the emulator with hk+start. Are you able to save and load states?
I just realized, it's working 
️. Somehow I just need to press the hk longer in mupen than on other emulators.
As on this post, hk+button gor special commands like save or load state should be working on mupen. https://github.com/recalbox/recalbox-os/issues/616 The only combination working for me is to exit the emulator with hk+start. Are you able to save and load states?
