Like other Firefox users, I've had the problem of not being able to save downloaded files to the Linux Desktop. The solution is supposed to be to change the "Save files to" to "Desktop". What if "Desktop" is already shown and downloaded files are not sent to your desktop? I learned by accident that Firefox has a folder named "Desktop" that has nothing to do with the OS "Desktop" folder. The solution is to click on the "Browse" button and navigate through the file system until the correct "Desktop" folder is selected. For example, my username is "lou" in Ubuntu Linux, so the folder name shown in the "Save files to" field is "/home/lou/Desktop⁩". Hope this helps folks.