Have a look at the attached screenshot.

File structure outline (or whatever is the proper name for the open box on the right of screenshot) is quite handy for navigating within your QML.. as long as you've got very different elements used. When you've got a dozen of rectangles and half a dozen of buttons, this view becomes nearly useless - hard to figure which button is where. It would be cool if that view could show item ids/names and/or just could display property values in a way the Outline view on the left of the attached screenshot does.