A question about collision.

I’ll first explain that I briefly used the UDK (Unreal Dev Kit) but I didn’t like that, anyway, if I wanted to apply a collision mesh for a model using the UDK I had to generate one in the UDK or model one in modelling software (Blender), to do this you had to make your mesh and a separate mesh (the collision) with a prefix of “UCX” eg: Mymesh and UCX_Mymesh and export as one .fbx model when imported the UDK would understand the prefix and use it as a collision mesh.

So can something like this be done in Unity?

TL;DR? Am I able to model collision mesh (out of primitives) in my modeling software and export with the mesh of the asset?

Yes, you can do this, by simply importing both and removing the renderer on the low-detail collision mesh. It won’t do it automatically, but there’s nothing stopping you from writing an editor script to implement the functionality you mentioned in your question.

You can also create a collision mesh out of primitive colliders inside the Unity editor. This gives you somewhat more reliable colliders, but is a little more tedious to do, because you need to set up your scene in the editor once you’ve imported all your level models.