I can't run the game in a window - only in Fullscreen

[Mudbill]

I don't have my Mac in front of me to see, but try this:

Open Finder, hold down the option key (alt), then click the Go menu at the top bar. There will be a hidden "Library" option when the key is held. Click that. You can also right click Finder and hit Go To Folder, then write "~/Library" without quotes.

Open Application Support, then find Frictional Games, then Amnesia, then Main.

Find the file called main_settings.cfg, and open it with TextEdit. Find the entry that says FullScreen="True" and change it to False. Save and exit.

Try again now.