Layers across multiple mixes

[kiwi]

I avoid using Mix's 1 and 2 as those are default tied to Screen 1 and 2 IIRC, but it always gives issues so I normally start at mix 3.

Mix 1 and 2 are tied to screen 1 and 2 if you have them in "full screen mix" mode, but they aren't set to this by default.
Otherwise they function the same as any other mix.