Your question prompted me to look back at photos we took on our balcony (Cabin 9092) and the divider does not look like it moves or opens in any way. It is a sort of opaque privacy glass with a metal frame holding it in place. Check out some of the photo galleries someone may have posted balcony pictures where you can get a better idea.
I know what you want to do, as on the aft balconies on the Norwegian Dawn the room stewarts could unlock the balcony dividers and the center was removable leaving kind of a door opening so you could go through to the next cabin's balcony.
