If you're anything like me, you've arrived at this blogpost after several increasingly frustrating minutes of clicking around the 'Advanced' tab of the Revisions Editor trying to understand why the CAD hierarchy isn't showing on the left side. How on earth is one supposed to select nodes/sub-assemblies for operations?? I'm sure the last thing you want is to carefully scroll through an explanation of the system’s structure before finally arriving at the answer promised in the title. For you, dear weary traveler, here is the solution:

1. In the Revisions Editor, select the asset you want to revise.
2. In the 'Simple' Tab, use the dropdown to select Target: Medium (any of Low/Medium/High will work)
3. Run the Revision by clicking Confirm.
4. When that Revision is complete, re-open the revisions editor and select the asset again.
5. Using the Base Revision dropdown, select the new revision you just completed.
6. Voila. Now you can expand the full CAD Hierarchy in the Advanced options and select sub-assemblies for operations.

With the answer provided, those of you who are even more like me may be wondering why that process must be done. For the few with a workflow involving multiple CAD types, there may even be a question as to why it must be done only for certain formats. Enter optional explanation:

When a supported CAD file is dropped into the Asset Library and processed, one of two things happens:

1. If its an .fbx , .obj , or .gltf it gets read directly into the library and made ready for authoring use in Create.
2. If it's any other format, it gets pre-processed by a secondary system which converts it into a format Create can work with, then it is read into the library and ready for authoring use. This secondary system is the same one used by the Revisions Editor.

Phrased another way, any CAD file not in the FBX, OBJ, or GLTF format has already been through one ‘revision’ before we, the authors, begin working with it. This is what allows the Revisions Editor (which is powered by that secondary system) to ‘know’ what the CAD hierarchy is and therefor act on specific sub-assemblies. This also explains why, specifically for FBX, OBJ and GLTF files, we must manually initiate one revision on the file before we can see the CAD hierarchy reflected in the advanced options of the Revisions Editor. The secondary system needs to ‘learn’ what the hierarchy of that file looks like. The five step process outlined above is how we teach it!