It would be awesome to have the option to add addition identical windows to your display that are independent of each other.
This way you could actually use Renoise on two (or more) monitors in a really cool, productive, and customizable way. Both windows are saved in the global view presets and perhaps the second window need not have the some uppermost features on it (File menu for example).
That’s multiple instances, rather than multiple windows working in unison on one instance. This solution for multi-screen Renoise has been suggested before and I think it’s one that fits the way of working well.