Sorry for completely missing your posts here…
When you check the “Add to VR library” checkbox, the game will be added to your SteamVR library AFTER a first SteamVR lanch (and not instantly).
So after ticking that option, once you launch SteamVR, the runtime will put the game into the manifest file (%steam install path%\config\steamapps.vrmanifest).
Now when you quit SteamVR, and PE comes back, it will automatically add the game to your SteamVR library (NOT Imports). It will be seen as a SteamVR game, but will get a SteamVR thumbnail on default (which you can change in Game Manager).
Now remember, doing it this way, you cant change the launcher for the game. because its not an “custom imported game”. Its just a non-SteamVR game added to SteamVR library, so its imported as a SteamVR game (but properly detected and launched in a different way than SteamVR games are laucnhed). Eitehr way, it will always start with SteamVR. And if you add command line argument, it should launch the game with the command lines provided.
It was long time ago I tested Alien Isolation mod. I will give it a try later tonight or tomorrow. Today Im a bit busy with other work tasks together with Kevin.