A YouTube video showing it: https://www.youtube.com/watch?v=mFhou-gHbWc
RetroArch v1.2.2 Multisystem playlist (aka My favorites) You can add your own playlists to RetroArch. In playlists folder create a text file and rename it Multisystem.lpl Open it and write this text:
(path to roms folder) \Super Metroid - Phazon 0.3.smc
Phazon 0.3
(path to cores folder) \snes9x_next_libretro.dll
Snes9X Next
1|crc
(path to roms folder) \SM64 StarRevenge Redone (Eng) (SM64 Hack by BroDute).zip
SM64 StarRevenge Redone
(path to cores folder) \mupen64plus_libretro.dll
Mupen64plus
2|crc
(path to roms folder) \sfiii2.zip
Street Fighter III 2nd Impact - Giant Attack (USA 970930)
(path to cores folder) \mame_libretro.dll
MAME 2015
3|crc
(path to roms folder) \castlevania_-_symphony_of_the_night.cue
Symphony of the Nigth
(path to cores folder) \mednafen_psx_libretro.dll
Mednafen PSX
4|crc
(follow 4|crc with two empty lines)
You will need two icons, Multisystem.png and Multisystem_content.png with the size of 256x256px, place your icons in assets>xmb>monochrome>png folder.
This way you can load games from retroArch xmb playlist like: MAME, SM64 hacks, Super Metroid hacks, Goodset roms,PSX games and more.