A huge relief to have a functional version of this essential feature in the new Firefox. The only piece missing from similar legacy extensions (unless I'm missing something) is the ability to nest a group of folders in a submenu. One of the main places I use to sort images has 20 subfolders, and listing all those on the main level of the menu would be impractical. Right now I'm just holding shift & opening the save dialog for that folder to choose the subfolder I want, but being able to nest the menu (assuming it's possible with webextensions) would help a lot. Adding some kind of character that could designate a specific folder as "always open the save dialog" (regardless of shiftkey) would be handy too. Thanks for developing this, keep up the great work!