Yep, as said its the screensets. Being Logic, it's a slightly backward way of working, but you choose the screenset number first (press any number 1-9 to select, hold down control for anything 10 and above, zero on its own doesn't work), then arrange the screen how you want it, accessing which window(s) etc.
Once you've got it how you want it, go to screensets again and lock it, and also name it if you want.