Tabs are possible. I've got a variant of them in my game. It's actually not very hard.
First, the tabtop object has a variable 'tabname' for its name, and should be the same as the layer name it corresponds to.
on tabtop clicked
set all tab layers invisible
set layer 'tabtop.Value('tabname') visible.
Set global value 'currentlayer' to tabtop value 'layer'
Then do a check with what layer's visible when the user clicks on a UI element. To do that, stick all the UI elements in a family, then give the family a variable telling what layer its on, and set it appropriately for each UI element. Then have another value somewhere else telling what the current tab is.
On family UIelement clicked
if UI element 'layer' is equal to global value 'currentlayer'