Steam supports network transfers natively now
Given that, no further work will be done on this application.
steam-export
A small cross-platform program written in Go designed to ease the process of exporting, import and copying of Steam games.
This applications specifically copies the appmanifest files into
the archives. This prevents you from needing Steam to "discover" or
"check" the files.
Steam only seems to scan libraries on startup, so any changes made to your libraries is going to require you to restart steam.
This process also seems to be much faster, and more reliable than Steam's built in backup tool.
Running the web server should pull up a local GUI that will allow you to download your games, delete them and install from remote URLs or local file paths.
Latest binaries for windows and linux are available here:
https://git.riedstra.dev/mitch/steam-export/plain/bin/?h=binaries
steam-export-web-windows-amd64.exe is probably the one of interest to most
people.
Windows "smart screen" may complain about the binaries since I have not signed them in any way. I don't currently have any plans to remedy this since it's a niche utility. I may PGP sign a set of hashes in the future if the additional security is warranted.
The server started when accessed remotely also allows people to download a copy of the application to easily install games from.
Screenshots:
Building
On Windows I'm using https://www.msys2.org/ for my development environment.
External Tools
Mostly for the frontend: