I only use mame, so I’m probably not the best for this. I could tell you my favored games based on console. Growing up, you either had Atari, nes, snes or genesis. So the separation makes sense for me.
To make an all in one favorites list. I have an idea. Not sure if it will work. Try it? Create a master romlist. Display filters based on equals custom tag. Then in other displays, add that tag to a rom. Would this work?