Just an image to show the inventory slots working, but not hotbuttons.
Those gem sockets are useless, can't drop a spell into them. Furthers my belief it's there as the image to use if a spell gets dropped into a hotbutton slot.
This is the result of changing <button item="HB_Button1> to <Hotbutton item="HB_Button1> and removing <pieces>HB_Button1</pieces> from the bottom. Had to remove from pieces because it resulted in referenced but not declared, revert to default.
Leaving them referenced AND <button item="HB_Button1"> results in Crash to Desktop with no reason in UIError.log