Transform and export TriangleMeshModel

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### Proposed new feature or change

With the latest development wheel, I am able to properly read complex models with multiple parts and textures in .glb format using the method `read_triangle_model`. I would like to be able to transform such a complex model like it can be done for `TriangleMesh` objects (e.g., scale, translate, rotate, decimate it), and then export the transformed model to another .glb or .obj file.
So far I can access the individual meshes and transform them separately, and I can then properly visualize the transformed model.
However, I am not able to export the result again as .glb or .obj

### References

_No response_

### Additional information

_No response_