I'll try to find a screenshot. I'm at work so posting all of this from my phone. It is difficult to navigate build mode at first, for sure.
Edit: I can't find a screenshot of the window selector. Maybe someone here can be kind enough to post one. I don't want you to have to wait six hours until I get home! In the meantime, look at the screenshot of build mode I posted above. See the three little boxes that are located between the house icon (where you choose window, door, roof, etc) and the actual object selection (in this case, the different premade rooms)? That is where your option to place windows By Room most likely is. There will be a selector for window height in that same area as well. At least that is my best guess without having the actual game in front of me.
I don't know about the paths, sorry.