I did it like this. I built a wall of five parts, left two short parts straight and carefully bent the other three parts into an arc. Then he pierced it with round and rectangular windows. The main thing here is to turn off the magnet. The round window (purple) fits well into the wall only in one single position - strictly perpendicular. You need to catch this short moment of window movement and release your finger from the mouse. And then the window moves to the right place of the straight wall. The other half of the window in the curved wall cuts a rectangular hole next to it, but it doesn't matter anymore. With two rectangular windows (green), you can add a gap in the curved wall between short straight sections. Then you need to save it to OBJ, rotate it properly, make the windows invisible, and save it back to OBJ. It turns out a section with a slit as in the photo. These sections can be combined into a group of the desired size. And a cornice without cracks is a wall without windows, also a separate model in OBJ. everything is combined into a single composition. Interestingly, when scaling different models of this cornice, for some reason, slightly different sizes are obtained, I fixed everything to single digits manually.
