Ah, you mean ECS screenmodes?
In that case, just copy all the modes over from your Storage disk, or just run all the files (VGAOnly first if you want to try with that). Then run a program with a screenmode requester and an escape key to quit, and see which ones work

Sorry I can't think of a program at the moment that'll do it but quite a few will, I think (MAME for instance). No need to reboot if you choose a program with a quit hotkey that you know!