I’ve started to add input configuration to RGUI. It only lets you configure gamepad atm. No regular hotkeys (except for RGUI menu toggle) are in the menu atm.
“Configure All” configures all RetroPad buttons in one fell swoop, kinda like zsnes. Binds should get saved to config on exit if config_save_on_exit is enabled. You can skip configuring buttons with Return. It also maps the joypad to the player automatically, so it doesn’t matter which joypad is used to configure (like Phoenix did).
It’s in the inputconfig branch: https://github.com/libretro/RetroArch/tree/inputconfig