When selecting files Shift makes a selection from first click to second click. This also works in combination with selecting somewhere else using Ctrl key and starting a new from-to selection from there. It is not possible to unselect files using the shift key in combination with the Ctrl key though. So if the first Ctrl+click does an unselect, so should the following shift+click command. Alternatively it may also be useful to have this behaviour of unselecting only occur while holding down Ctrl + shift key? Holding down Ctrl+shift may also apply a toggle to each file in the selection instead?