This. I've thought for a while this would be a great addition to Capture.
Being able to see a list representation of not just fixtures but also imported meshes and user grouped items would be a really powerful addition. Being able to rename these groups/items, and see what layer they belong to.
Something along the lines of the way the outliner in sketchup works, where once objects are grouped (or made into 'components') they appear as a selectable item. If they only appear once grouped that would reduce the impact on importing new meshes and handling those conditions.
I agree that it can be very difficult to keep on top of what is grouped together, what 3D meshes are part of the same model, and how groups are nested within each other.