The problem is non - existand when game maker uses just couple of layouts, but starts to be anoying with more complex, multi-level games. as in any game there are some conditions that should always work aside from whats going on on the screen (ESC button for quiting, fullscreen button ect). But i know we can import whole sheets into sheets but still theres no such thing as General Sheet with events that are always present - whereever we are in game.
i think having a Sheets for a whole Aplication (Global Sheet?) wouldnt hurt, and for 100% would make some peoples lifes easier and better organised ("OMG why movement stoped working???? [4h later after re-checking the whole event for errors for 1032 time] oh... right... i forgoten to include controls sheet in that layer...")
Did you know that you can have any number of event sheets and include them as you like? So you could make a Movement sheet and include it in every layout where you want the player to be able to move, for example.
I think this pretty much makes your suggestion obsolete, if I understood correctly what you were saying.
EDIT: Ah my bad. You actually want global event sheets so you don't have to include them, right? Not sure if that would be really feasible. Is it that much of a pain to include what you need? I may be wrong.