New user here, questions, issue and suggestion

[Waifu4Life]

You could probably write a powershell or python extension to mark them as installed https://playnite.link/docs/api/Playnite.SDK.html

But I don't understand, why would you want your unninstalled games to show as installed?
Why are you not importing them as unninstalled, which is the correct and supported way? It's not a bug or lack of feature, Playnite expects for you games and clients to be properly set.

Modern games (from the past 10 years or so) do not need to be "installed" in Windows to run. My 500+ games are on a 6TB HDD. When I format my SSD to reinstall Win10 and install the game clients (GOG Galaxy, Steam, Itch), I just tell them where their proper game directory are and that's it, they find their games. Playnite has NO issues for my "not installed in Windows" Steam and Itch games, only my GOG games. The only way it sees my library is by telling it to see my games that are not installed, it acts differently with the GOG plugin than it does with Steam or Itch, hence why I say it's a bug or missing feature.

Also, regarding my previous post with a solution, scratch that, as soon as you close Playnite, it forgets everything. This either a bug or the fact that it's a game that's suppose to be handle by the plugin erases everything from the database. I also tried manually linking the EXE, same thing close the program. Guess I'll have to make them independent of any game clients in order to configure them permanently.