Combine effected area of multiple masks to create a new mask so I can set the effects as one?

I agree.

There seems to be no way (incredible, and sad) to combine (add, subtract, or intersect) ANY two masks.

Subtract Mask 1 from Mask 2.

Ought to be simple.

What am I missing? And, yes, I know I can always subtract a Sky, or a Subject. That's not what I asking. ANY two Masks. That's the deal.

The new (version 11) masking method does allow you to combine multiple kinds of selection, by addition or subtraction, and to associate the whole lot with a single set of "effects".

Only when you want to apply different "effects" do you need to maintain separate masks. 

As an example, you might select Subject, invert that so you select only whatever is not subject, then select Sky as a subtraction from that, to produce a complex selection of "all the background around the subject, but excluding sky areas", and apply some adjustment to all those parts of the photo. Then you might make a second mask within which there is only a Sky selection, and apply some different adjustment to just those parts of the photo.

Equally, you might use non-AI selections: say, a gradient mask and then adding onto this, some brushing and then subtracting from this, some other brushing. So the gradient, the additive brushing and the subtractive brushing can each be further edited in its own right, but their combination will then update and the adjustments being applied onto the photo will update correspondingly.

Or, of course non-AI kinds of selection and AI kinds of selection can be combined together as needed.

The fact that this consists of multiple "layers" of selection all combining by Add or Subtract logic, does mean that if you then wanted to invert the whole lot, that will involve not only inverting individual parts, but also switching the logic of how these are combining together - by changing from Add to Subtract, or from Subtract to Add. But you won't want to make both kinds of change to the same "layer". Taking the first example above: "Subject (inverted) minus Sky" would fully reverse as "Subject plus Sky". The Subject part getting 'switched' in its effect by no longer inverting it, and the combining Sky part getting 'switched' in its effect by Adding that rather than Subtracting that.