1: When “Defined Menu” list has a scrollbar, Drag and drop an item to move it. Then move mouse (released) to the border of the list. ** The list will scroll.
2: Select item A in “Defined Menu” list. Drag item B. ** While B is being dragged, A is still highlighted. This could be confusing.
3: I think an empty Popup item should show the node image initially and always, otherwise it looks as same as a Command item but doesn’t respond to double clicking. it could make one confused for a while.