Grouped Items Won't Properly Show in Trigger Wizard

Hi,

I really enjoyed Dave's presentation on 5 Ways to Customize Drag-and-Drop Interactions in Storyline! 

I'm trying to build a similar interaction to the one he built. When I try to add the "hidden" state to my grouped text boxes and shapes so that they disappear when dropped on the brain character (see screenshot below), the trigger wizard does not recognize my grouped items and instead lists them individually.

Can someone help explain what I am doing wrong? Much appreciated!