The ability to group a number of selected areas, so you can quickly re-select them at a later point to make adjustments.
Currently you have to manually click all 267 areas of someone‘s hair a second time in order to change the hue just a tiny bit.

I could see this work as a bunch of little numbers below the Single Select / Multi Select buttons.
Select a some areas, press 1.
Press 1 at a later time to re-select them.
Long-press 1 to have the option to delete the group.

Thanks for considering this idea.