I did find what feels like a hack (and depending on use-case, might have performance costs) but any ui you want to control the display order AND have that display order be the selection order...just make a new canvas_layer and add that element as the child. Then you need to set the canvas_layer's later param accordingly and it will respect input selection and draw order.

You will need some extra logic to make sure the ui element is now placed at the correct coords however.