Invert/Duplicate Mask?

Hey, simple issue- I can’t figure out how to do either of the following, and either one of these would solve my problem. I need to either:
-choose to invert a mask applied to a video (no simple check box for that anywhere??)
-duplicate a complete mask (in order to basically make an inverted version myself)
There seems to be no way to do either one of these (simple) things, and Google-searching the issue finds NOTHING. Odd, considering those are simple functions I’d expect a lot of users to look for - apparently not, unless I suck at using Google just that badly.

or use an invert node directly after the mask node.

Had the same problem with the duplication. Solved by:

Copy the file and append the mask from the copy.