They are actually ones I've added (I assumed Ctrl-F4 was there by default as it's the standard for closing tabs in an MDI application), but they do work once so added (when docked into the multidock).   I think I probably added them because it annoyed me I couldn't close them easily!  Annoyingly, you need to add them to every view that you're going to dock.
 
	To be honest, it doesn't annoy me so much now as I've got workspace(s) set up to not dock anything except the views I really want docked, so I don't use the shortcuts now.  And it doesn't annoy me as much as Melodyne always appearing in the multidock, irrespective of the state you left it in.