Back in a day Cubase had multiple arrangement windows per project. That’s before the VST version of Cubase.
I think this feature could be very useful especially for Film Composers. That’s because a composer could work on a certain cue, then switch very quickly to another cue (a different arrange window), and not have to reload all the instruments. Reloading instruments each time may take few minutes at times, when a composer is loading a big template. This multiple arrangements per project feature, when done right, could be very useful!!!