From Dean Hall, a.k.a. Rocket:

ChrisH has also been cooking! This is a very WIP image showing this work off . It is still very WIP and chris has a lot of changes coming, this commit was moslty made so he could avoid merge hell going forward.

What does this mean?

Well pretty simply it means we can have multiple application windows open, on different screens and such. This is helpful if you want to have a window on one screen that shows, say, the moon, and then your vessel on another. It is also really useful if you want to make your own peripherals for the game - Flight Sim uses this a lot with aftermarket MFDs and other devices.

More to follow with this!