The Nintendo Switch recently got a new update which introduced Button Mapping. I think it’s a great implementation and very intuitive to use thanks to the image of the actual controller with all its buttons labeled.
Personally I like Retroarch’s current Controls Remap option and find it simple to use. Though I have read some user comments that have problems getting used to it. So I think a similar design as the NSW Button Mapping would be a great fit for RetroArch, providing an even easier configuration with a better overview than the current list format:
