Unmark multiselection when clicking on already marked

Hey.

It would be great if the marking would deselect if you click a already marked area when you want to multi select.

Say you want to mark 10-20 custom markings with the cmd+(mouseclick), if you miss the last one you will need to do it all over again, so it would be great if you could click a marked selection and then it would deselect.

Great product by the way.. :)