Cannot close main application window with keyboard shortcut
When there are no documents open, it's apparently not possible to close the application window from the keyboard (e.g. with the traditional shortcut Cmd+W). The Close option is disabled in the File menu.
Cmd+W is used to close the documents, if you want to close the application, please use Cmd+Q
Kate Playford commented
Is it possible you've got Application Frame active?
Go to Window menu and uncheck it, it's one of the options near the top.
Kit Grose commented
I don’t want to quit the app, I want to close its window. You can close the window with the mouse but not the keyboard.