David Pensato asks how to delete a domain attribute on an outline node. My answer was to create a new node, move the subs of the old node under the new one. But that's too clunky and I think we know how to do this now.
New command in the World Outline sub-menu of the Outliner menu, Clear atts.
After confirmation, we delete all the atts, except for created and pgfnum.
If there are no atts to delete, an error dialog appears saying "Can't clear atts because this node doesn't have any."