Just press alt+enter to toggle between fullscreen and windowed.
To answer your specific question, it is only present in the debug config, which you access by pressing ctrl+shift+f12, and then clicking on config. Or you can edit the settings.tml file in your user directory with a text editor. But really, alt+enter.
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To answer your specific question, it is only present in the debug config, which you access by pressing ctrl+shift+f12, and then clicking on config. Or you can edit the settings.tml file in your user directory with a text editor. But really, alt+enter.