Cmd+Q is a standard shortcut to quit the app entirely, I'm not sure if overriding it is a good idea. Try using Cmd+W (or Esc) to close the window without quitti

Cmd+Q is a standard shortcut to quit the app entirely, I'm not sure if overriding it is a good idea. Try using Cmd+W (or Esc) to close the window without quitting the app.