Invert color tool in the Masking feature

We have a circular screen we are using for our missions convention to project a moving globe, so we want to mask out everything except that circle. Unfortunately there is no simple way to do that. With the current masking tools you can add a circle, but it masks out that circle you create instead of masking out everything but that circle. So in order to create a circle mask, we need to spend a lot of time using circles and rectangles to mask out everything but a circular shape, but the problem with this is that you can never make a perfect circle this way, you end up with jagged borders and a circle that may look like an egg or an oval. The fix here could be an inversion tool that simply turns the masked out area to the masked in area, so it could just turn black to white and white to black. If this tool existed, I could simply use the ellipse tool to create a single circle in the middle of the page, invert the colors, and voila, I would have my circle mask in seconds. (P.S. I was able to invert the colors in the meantime for our event by searching for the .maskx file mediashout created and opening it and changing the hex codes of the colors of the shapes, but that took some time and effort to figure out on my own.)