Nothing happens if pressing entry in the menu or using the two shortcuts.
Broken in preview 5.3 260, was still working in Preview 5.3 214.
Edit: just now found these two windows empty behind a renderer, without any ui elements but with just the title. Something doesn’t seem right, but after restarting vvvv it works again. Before I was closing my running project, tried with an empty patch, but didn’t restart vvvv it seems. Will report back if it happens again.