I've been doing a lot of 3D design in Codex GPT 5.5 (I found Opus 4.7 wasn't as good - haven't experimented much with 4.8 or Fable).

OpenSCAD is a parametric CAD programming language, and the models know it well.

The biggest challenge is communicating words like "inside" and "above" to the model - inevitably it's idea of which direction is which is often different.

I can't say I've done anything very hard, but for things like ESP32 cases, or parametric rod connectors it is great.

You can do things like "add snap connectors" and it'll do a great job.