@wsamael said in Need help for overlay in retropie 4.5.1:

I can configure in retroarch menu but it's only one overlay by core ( so sega megadrive and sega master system has the same overlay )
How can i configure it system by system with a different overlay for each ?

The thing is, those systems use the same emulator - so use different emulators for those system. Try lr-genesis-plus-gx for megadrive and lr-picodrive for mastersystem so each system has it's own libretro core that you can configure differently.