It's the same library as GaudiGalopin3324 already mentioned and gave a link to. I just provided the oroginal link on Sweet Home 3D.I haven’t seen this library of light shapes that Keet mentions, but thanks for that Keet! I’ll definitely install that!
You can solve that by placing the windows in a vertical wall and export both wall and windows. Then import it and tilt it to the correct position. This works assuming your windows are imported as "Door or window" so they cut a hole in the wall. You can set a d value of d 0.3 or d 0.4 for the glass material in the MTL file to make it transparent.As you can see, there are no windows, but the ILLUSION of windows. <As when I tried to create them as windows, positioning them on diagonals made those annoying 90 degree corner angles appear, and I couldn’t have that. But I digress.
As when I tried to create them as windows, positioning them on diagonals made those annoying 90 degree corner angles appear, and I couldn’t have that. But I digress.I'll leave answering the light question to GaudiGalopin3324, he's much, much better at that than I am. I do know that if you create the windows like I mentioned that you can place a light behind them that will shine through the glass (if your glass material is transparent).