P: (Masking) Group Masks (incl Auto group masks that belong to a preset)

That would be great. 

This image contains three vibrant fabric entities plus everything else. I wanted to individually adjust the fabrics, then adjust everything except the fabrics, then adjust the image as a whole.

So I created masks for each of the fabrics. Each of the three fabric masks contained between ten and twenty individual object entities, because the interact and intertwine with the background and each other. So far so good. 

Having made my individual fabric adjustments, then came the trouble.

My next step is to combine or group the three masks, then select the inverse of the group so I can adjust everything except the fabrics. It seems you can't do this. There is no way to group or combine three separate masks. Nor can you select more than one mask at a time. 

My solution was to duplicate one of the masks, and call it 'all fabric', then copy and paste the individual elements of the other two masks into it. This is extremely time consuming as you cannot select/duplicate/drag the individual mask elements as a group. You have to duplicate and drag them one at a time it seems.

Having done that, I could do what I wanted. Invert the all fabrics mask, bring the background to where I want it, then deselect the mask and finish adjusting the image as a whole. 

The inability to combine/group masks, which is common usage in Photoshop, seems odd?

It would be great if, in the mask tool, you could combine individual masks into a single group. Or, select multiple masks, and have subsequent actions act on all the elements of the selected masks. 

It would be great to group mask layers (basically like folders in PS).

For example, masks for creating film borders on images contain masks for the effect. Being able to group the masks as one Group would be helpful so I could turn that Group on or off, rather than each individul mask. Same idea when masking several different people in the same image - keep Subject #1's masks grouped from Subjst #2's masks, et al.

I would like to see an option for grouping masks, similar to Photoshop's layer grouping, and the ability to adjust the strength of the effect using a slider, in a future update of Lightroom. I believe this would be a fantastic feature!