It works - but as it was little more complicated in v.15 then in newest 16:
- you have to draw your window with 3D elements,
- open 3D window and set axonometry (elevation from top),
- use command Save 3D model as... form File/Libraries and Objects,
- choose Window for object type from next window.
That's all for saving rectangular windows.
Best
Rafał
//Archicad since 4.1 version
//MacBook Pro Retina 2019/2.4 GHz/Intel Core i9/32GB RAM/Radeon Pro 5500M 4GB/macOS 13.6
//Razer Intel i9/2.5GHz/32GB/Nvidia RTX 3080/Windows 11 Pro
//ArchiCAD 28/Twinmotion 2024