I have basically zero knowledge of Unity, but I wanted to check how hard it would be to create some basic asset geometry for mods. However, it turns out that the assetbundles that are used have been deprecated since 18.2 and that you can't export those any more. The Unity docs refer to a demo package that includes the assetbundle support, but I can't find anything about exporting.
How should you do this now if you're starting from scratch?
How should you do this now if you're starting from scratch?