Great shortcut! Now if only the Pixel persona in Designer were able to do the same thing. View > Show Pixel Selection doesn't exist in Designer, unfortunately, and I do a lot of pixel work with Designer where this would come in handy (mostly cut & grad coloring).
An obvious workaround for my use case is to switch to Designer persona and draw the selection area using the pen tool, then switch back to Pixel and paint over the new vector shape; it serves the same function as far as clipping goes. But it means that selections based on pixel information (for example, using the selection brush tool) still must be made using pixel tools, and the marching ants remain in the way visually. It would still be great to have the option to show and hide the pixel selection the same way it can be done in Photo.