sync windows in forward view for two monitors

I remember there was a way to open a second window with [ key, drag it to a second monitor, and create a wide screen view from in the cockpit. You had to adjust the second window and line up the cockpit, which wasn't easy, but then you somehow sync the windows. So when you went back to view one and rotated the view, the second window would move at the same time in a coordinated way.

I know this has been discussed ages ago, but I forget how to do it and a preliminary search didn't give any results.

Does any know how to do this?

Thanks