I found the solution.
There is a preference:
After adding the type there, a new icon "delete" appears in Active Workspace after click on the object.
Thanks for posting the answer to your own question! We have been shaking our head on this lack of functionality.
1. How did you find this preference? It doesn't appear to be documented anywhere.
2. We tried it out on a dataset. However, it appears that the dataset must be cut from the ItemRev before it can be deleted. This is pretty cumbersome for the user. Did you find a workaround for this?