Queue the FF is not tread safe jokes (and only that, not a flame).
OP: you can use Firefox Sync. There is a cloud version by Mozilla but also a WSGI app you could host. I know it is not a 100% solution, but what was recommended to me when I asked during FF alpha and beta testing with stable way back when.
I lack the necesary knowledge on how to correctly install two different FF versions and have them accesible with their respective icons. In my case, FF dev version and the one discussed in the article to help out with bug testing/development.
The issue is since I'm on Debian, auto update does not work. From my limited understanding, I would need to install FF 57 in its own directory. For this one I don't need a profile. But I don't know how to install it and have it accesible either by command line or the FF icon that comes with the browser since I already have my main FF I want to keep.
The second part is regarding the profile, sync with the other browser I recently installed.... I was about to go down a mental rabbit hole :)
The problem is, the lack of noob friendly documentation. I know I could figure it out if I research the issue through different topics on Linux administration. I was hoping that maybe someone knew of a tutorial which talked about the different steps on how to install Firefox on a nix system, explaining the different concepts as if I were a five year old. The best I've managed to find is a tutorial laying out the steps. But it didn't explain the concepts behind those steps.
That tutorial mentioned how to replace debians FF from the repo. But whenever a new version comes out I would need to delete it and unpack the new one, linking it to the old icon.
I hope it's clear now. Thanks for the reply.
I literally just downloaded the zip file (or maybe a .deb?) and unzipped it in a directory in my desktop. All I had to do after that was make sure I didn't have both browsers open, and everything worked properly. They both used the same profile, and the tabs I opened in nightly were available in stable and vice versa.
I did nothing more than unzip the browser, and everything works perfectly.