Selecting subject in the new Lightroom release is great...but no automatic tool is perfect. After creating a subject selection mask, I often Add or Subtract with a brush to clean it up (There is currently no "Refine edge" function, which would be awesome, by the way). My problem is this--Now that I have the Subject selected, I duplicate the mask so I can select the background. But the Add/Remove brushes don't work properly and must be converted.
Instead of duplicating the mask and going to each element to invert, convert to add, convert to subtract, I would like to see an option on the mask itself to "Flip" it. The Flip at the top level would invert the select subject mask, and convert the Add to Subtract, and convert the Subtract to Add. Then the mask would be a perfect inversion in one step.
You would have to consider how it would behave with the other mask elements--I was only considering the select subject/Add/Subtract.