But I’m curious, how does it work? I see no way to add a jam manually, and add games to jam. How do you configure it all?
Viewing post in Using a Jam Player, maybe?
On the repository I linked, there's a separate Jam Packager project, that handles editing and saving all the relevant metadata (also some quality of life features like automatically unzipping all the ZIPs of the downloaded entries). Once you save the metadata, you can open the Jam Player from within the folder which has "jam.jaminfo" file and it'll show the entries correctly.