P: Merge (Flatten) selection masks in Camera raw and Lightroom

Hi Adobe, 

Masking in Camera raw and Lightroom is great, especially the possibility to combine selections (with +Add, -Substract). However, it has been my long time frustration of slow down performance of the application when combining/stacking complex masks  based on  several AI powered "obect select" or "select people", "select background" and similar. 

Feature request: please add possibility to "flatten", "merge selections", you name it,  stacked selections into  single masks.  In UI ith can be  next to "invert mask". 

In other words for instance instaed of:

Mask1 

  +Select subject

  +Select object

  - Substract background 

  +Select People

  -Substruct gradient

... etc

merge mask!:

Mask1

 +Merged mask

Save the planet from overheating by our PCs.

Thank you