Does not work on Mac OS. Tried click after click, but nothing. Using Firefox 64.0 (64 bit). It sounds like it would be a useful extension. Hopefully a future release will work on Mac.
It didn't even come up with the save/open dialog and from there, the choice of directory to save it to. It just did nothing at all. Click after click, nothing. Didn't update download listing bar, either. Using Firefox 56.0.2 (64 bit).