Quiggling

The same issue affects Wii and Gamecube. When I tried to use Retroarch through Launchbox, any time I try to launch a PS2 game it says "pcsx2 is the best way to play" and asks me to either download that or add an emulator. I tried assigning it to run them with retroarch but in the associated platforms list PS2 is not an option. I've found no way to manually add PS2 (and Wii/GC) as an associated platform. Is their anyway to do that or do I need to just move back to using only Retroarch standalone? I like the front Launchbox front end so I'd like to find a solution.