It's still somewhat functional but it no longer saves to the correct folder anymore. Mozilla's update broke this addon. Also... it uses regular expression codes, such cancer; no one should be forced to use this.

Too complicated. Maybe advanced users will have an easier time with this add on, but it's not for coding illiterates like myself. With unclear directions, this add on is unusable,

I sat here for over 6 hours trying to get the code you provided to work. Unless you show Screen Capture of how to use Download folder to mklink /j to another drive folder and a actual working code that does not give red errors like "mklink /D C:\path\to\symlink D:\path\to\actual" I know mklink /j \default_download_dir is right, because C:\Downloads does not work. Plus Everything on internet says you have to do this Admin Command Prompt. Which I got to work. Question remains since you do not show or produce no REAL example of how to display such in on SaveIn Menu . Sure I can Create many new folders in Download folder but What I save I do not want in the download folder. I am not one who needs to Save things to Newly Created folders. I can understand adding Existing folders to SaveIn.

C:\Downloads > D:\ Picture Folder

"A symlink is needed to save outside the default download directory" ....
(mklink /j \default_download_dir D:\Picture_Temp\New_Sort_Temp ) ERROR.

(mklink /j \default_download_dir \Picture_Temp\New_Sort_Temp ) ERROR.

Wiki
Example:

mklink /D "C:\Users\\Appdata\Local\Plex Media Server" "G:\Plex Media Server"

" Quotes" and : Red Error