(OrderedCollection with: Transcript with:5 with: #X) snoop.
|d| d := Dictionary new. d at: #a put: 'a'. d at:#b put: Transcript. d snoop.
If you try to expand a line containing an object that has no children, a marker appears by its name. (Depending on which platform you are using, the marker might be an omega, a left angle bracket, or some other symbol.)