Librewolf would need to ask permission to a folder (for the standard downloads folder for instance) or it would need to show two save prompts when downloading two files (isn’t that what it does already?)
The “two files” thing only applies to applications that ask access for one file (say, an mp4) and also want a second file in that same directory (say, a matching .srt). That can be worked around by selecting multiple files in the file picker, but that does pose for an annoying restriction. I don’t see how a browser would be affected by this, though, as browsers don’t tend to also send secondary files when you upload something.