... (how) is this possible?
 
Right now Melodyne always opens in the docker, where it is completely useless due to the tiny amount of space. I would therefore like to configure it to always open on the second monitor and in fullscreen mode.
 
Any help appreciated ...

I do not know of a way to have Melodyne instantiate outside of the multi-dock other than to add it to the Utilities menu (there are some posts here outlining how to do this with soundforge and requires a registry edit). Doing this actually passes the audio to Melodyne and Melodyne opens in stand-alone mode. Makes edits, save, and exit, and that data passes back into SONAR. Edit: Actually Melodyne may already exist in the Utilities Menu, since I never recall adding this on my machine. Melodyne will be passed the active clip (or potentially entire track) via this method.
 
However, you can undock the multi-dock and put that on a second monitor maximized. Then when Melodyne instantiates it will still be inside the multi-dock, but it will already be on the other screen and maximized. This may be the simpler solution to try first.

If you haven't already, undock your console and put it on the second monitor. I believe Melodyne will go wherever the console is. In my case, it always opens to the second monitor as a full screen tab.

You can move the whole multi dock to the other monitor and open it full screen then anything that starts in the multidock will display there.

mudgel
You can move the whole multi dock to the other monitor and open it full screen then anything that starts in the multidock will display there.

 
But it only remains on the second screen while there is something docked within it. As soon as you close Melodyne (or Bounce to Clips, which automatically closes it), the Multidock reverts to its original position in the main window.

Not if you unlock the screen set in which you move the dock and then lock once you're done.

mudgel
Not if you unlock the screen set in which you move the dock and then lock once you're done.

 
I've just tried that. It didn't work.

The multi-dock automatically closes when there is nothing in it. The way I get around this is that I always have the console view in it, and I keep the dock full screen on the second monitor. That way, if I've got a melodyne window open in the multi-dock, and I bounce the clip, the melodyne closes, but the dock doesn't.

Yep what john t said

Haha! Left out a step didn't I. As John T said keep the Console in the Multidock. I've had my setup for so long I forgot. It's what I call my default screen set 1 so I can always get back to it.