Digital Light & Color

Reverse Order command in Mask gradients settings does not reverse the mask overlay.
Black, white and grays get swapped on the color line, but the mask overlay is left unchanged.

One more comment.
Inverse Colors command does nothing as well. Since only Black, white and grays can be used in the mask gradients, is this command necessary?

After clicking Apply, further changes such as Reverse Order do not take effect until you click Apply again.

It is on my list to make Mask Undo of tools with Apply buttons work in two stages - first Undo to undo the last Apply but leave the other settings intact and a second Undo to revert to the previous operation.

Ok, I can see it now. However, the second Apply just adds to the previous mask, making it full mask, instead of exchanging the masked areas.
At least, if I get it right.

Once you do the Apply you need to do an Undo to remove the old mask before applying a new one.

Yes, so it means to redraw a line or an oval. In this respect it is different from the Gradient transformation. I guess that is what confused me at first.