I've been using the accessibility keyboard, and switch control to build custom keyboards and custom panels with custom buttons, since these are MacOS features no additional software is needed.
i create custom buttons to trigger KBM macros, but I use the trigger by key options.
since this is native apple feature, and its a great (free) replacement for Elgato Stream Deck. I'd like to suggest a tighter integration keyboard Maestro with apple accessibility keyboard and switch control.
KBM managed to have integration with Stream Deck. but I believe that Apple Switch control and custom panels are a much better option, also its free, and as an added bonus can in fact be a great feature for people with actual accessibility.
Welcome, Nelo!
I'm really intrigued by what you're saying here. I teach accessibility in electronic documents and computer systems, and I'm (obviously) Mac-based. I'd be interested in talking to you about this idea in great depth, if you have time. Please DM me.