Problem: When downloading/saving files of various types (.txt, .pdf, .mp4, .png, .mp3, .exe, .zip, etc) in Firefox, I find it cumulatively tedious and time consuming (# of clicks) to always have to renavigate to my intended save location in the file download dialog box (e.g. Alternating between downloading .png or .mp4 files).
The last saved location as the starting download location in the file download dialog box is useful but very limited.
Typically, I'll always want to download video files (.mp4, .mkv, .mov, .avi, etc) to my user Video files location (e.g. \Users\%USERNAME%\Videos\ on Windows or \home\$USER\Videos\ on Linux ) or a subfolder underneath that location for easy organization and retrieval later. Similar situation with image files (.png, .jpg, .webp, etc in \home\$USER\Pictures\ on Linux) or document files (.pdf, .txt, etc in \home\$USER\Documents\ in Linux).
I also notice that defaulting to the Downloads folder for all file types tends to reinforce bad user habits (one click download to the "dumping ground" that is the Downloads folder).
Suggestion: In the about:preferences menu of Firefox underneath the Applications/Downloads section, I suggest adding in a new column/configurable field to allow to the user to specify the default starting location path for each file type. Perhaps set the default paths to the system default locations (e.g. \home\$USER\Pictures\ on Linux for pictures files).
This also helps alleviate Downloads folders from becoming bloated wastes of gigabytes and a mess to sort through, retrieve files and organize later. An ounce of prevention equals a pound of cure as it were.