forward delete not working within Firefox dialog boxes

If I go to save something from within Firefox (on MacOS desktop browser), if I try to forward delete some characters, nothing happens. I can go to the address bar and forward delete characters within a URL, but doesn't appear that I can do so in other dialog boxes within Firefox. I've verified issue persists in debug mode as well as standard mode (and just re-freshed firefox within the last day and thought that had resolved the issue until realizeing forward delete will still work in URL field, but not in firefox dialog boxes like the save as window when downloading something.