I installed Star Citizen, a very large game and one I’d really rather not have to download again, via Lutris on my previous installation. I reinstalled with straight Arch recently, and I’m wondering how I can get Lutris to see Star Citizen again. I read something about a config folder, which I did not unfortunately create a backup of before installing Arch. How can I get Lutris to see the game that’s installed here?
Incae you haven’t solved this yet, just install it again and then tell the RSI launcher to verify the game files. It will see they’re all there and you will save yourself a tonne of downloading 
I believe the answer he was looking for is something along the lines of “use ‘Add game…’ dialog to register the game in Lutris (providing it the install path etc.) and it should work, if there’s any custom settings required like specific Wine version you can find that info in the Lutris game install script”.
Although if the game itself has a tiny install size and all the heavy files are downloaded by launcher, letting it check the files first would likely work, too.