OpenCAGE can work with more than one Alien: Isolation install — for example a clean Steam copy for playtesting, a separate modded copy, or installs from different storefronts (Steam, Epic, GOG, and so on).
Each install is registered in the Game Directory Manager. One install is your default (what OpenCAGE opens on startup). You can also open additional editor windows pointed at other installs at the same time.
From the main OpenCAGE window, open Options → Manage Game Directories.
Click Register New Game Install, then locate that copy's AI.exe. OpenCAGE checks the folder is a valid Alien: Isolation install and shows the detected platform (Steam, Epic, GOG, etc.).
You can't register the same path twice. If the folder isn't a valid install, registration fails with an error.
Each registered install has a Set As Default button. The default is the install OpenCAGE loads when you launch the app normally from Steam.
Set As Default does not switch the install already open in your current window — restart OpenCAGE to load the new default. To work on another install immediately without restarting, use Open Editor instead.
On any registered install, click Open Editor to start a separate OpenCAGE window for that path. Your original window keeps whichever install it was already using.
While that second editor is open, Open Editor for the same path stays disabled. Close the extra window to free the button again.
Game Directory Manager is only available in the primary OpenCAGE window (the one you launched from Steam). Extra editors opened for other installs can't change the registered list — manage installs from the primary window.
With several editors open, Options → Misc → Show Game Platform can help: it appends the detected platform (e.g. Steam) to the window title.
Every editor window with the Viewport enabled starts its own 3D view, which uses more memory and can slow level load. That adds up quickly if you keep several installs open at once.
In the Game Directory Manager, enable Launch other editors without viewport (saves memory usage). When that option is on, windows opened with Open Editor start without the Viewport.
You can also disable the Viewport for the primary OpenCAGE process via Steam's launch options. See the Viewport docs for that.
