On Editroid 1.2.whatever you could easily spot and use the vertical room button.
I guess I missed it.
But seriously, there is no vertical room button. The way the vertical/horizontal scrolling works in Nestroid is it simply switches from one to the other each time you go through a door. If you are in a horizontal room and pass through a door, the scrolling goes vertical, and vice-versa.
The exception is the special doors used to connect a horizontal room to a horizontal room. (Or, rather, it's the doorway, a.k.a. door connector I'm referring to, not the door itself.) In the original ROM this would be structure # 4 (the normal door is structure # 3). There is absolutely no way to connect a vertical room to a vertical room.
I had been working on a hack to allow Editroid to specify the scrolling for every screen on the map. This would make scrolling infinitely easier (you wouldn't need to use the right kind of door, and would be able to do vertical-to-vertical). Right now this is just behind the back burner because I'm already working on too many things.