Oh okay, another person that feels it is a security risk and maybe why Avast flags Save In on occasion. Save File To was never flagged as a security risk and it did far more than Save In does.
Before FF changed to their new version Quantam, I used to use the Legacy Extension Save File To which allowed all the things I'm inquiring about via FF. The main thing I liked the most is being able to DL a file directly to a drive without it creating a folder. So say for example I need to update a program. I would click on the Save button and Save File To would allow me to DL the file to any location I want. It also had a default drive you could set it to using FF directly. I don't use JDownloader for that type of DL.
BTW, one of the reasons I use JDownloader is to DL things from YouTube. Yes I'm aware that there are many other programs and ways to DL things from YouTube, but that is only one of the reasons I use it.
I started to do some searching about the issue from my OP. What I've come up with so far is the following.
Save In is a valiant attempt to recreate all of the options/functions that Save File To had, but because of FF v57 WebExtensions API, it appears it cannot replicate all of the Save File To features.