Also, keep in mind that anything you have set to global is created for the duration of the game once it is created unless you specifically destroy it.
For example. Drop a button and a text on a layout. Create another layout and drag the same button and text onto it. Have the button on layout 1 go to layout 2 and have the button on layout 2 go to layout 1.
If you run it in the debugger, and expand the trace for the text object, you'll see that when you click the button to switch layouts, it creates an 'instance' of the text for each layout and destroys it when you switch layouts so that only one instance of the text exists at any one time even though you have it on 2 layouts.
If you set that text to global though, it still creates a new instance when you switch layouts but doesn't destroy the one from the previous layout so you end up with two instances, just different UID's.