Here's a simple, but helpful enhancement idea for the "Hue/Saturation" adjustment layer:
In its properties it would be great to see a little indication next to the color ranges in the dropdown list of color ranges ("yellows", "reds", "blues", etc.) that shows which of them have already been manipulated. It could be as simple as an asterisk "*" next to "yellows" if it contains adjustements. Currently I have manually flip through every color range sub-setting individually to see if it includes changes.