This company makes windows that convert to balconies

HofmanDujardin makes Bloomframe windows that work like a Murphy bed, opening up into a balcony. The only disconcerting part might be the pane of glass that doubles as a floor. That might trigger guests' vertigo, and walking around on it seeks it might scuff or scratch it. I would cut a piece of carpet for when it's down, or at least make guests take of their shoes.

Here's another demo and a Chinese ad:

Image: YouTube / HofmanDujardin