keyboard shortcut to make current item the topmost child of the (parent) item below it in the grid (e.g. Shift-Alt-Right)
When you want to make an item the topmost child of another using just the keyboard and you can't / don't want to use copy / paste, it's very tedious: move under target item, press Alt-Right, then Alt-Up many time until you reach the topmost position. How about instead: move just above target item (just below it would be fine, too) and press Shift-Alt-Right.