Check boxes created as custom metadata fields persist, even though the metadata category was deleted. The boxes continue to show with the beta 32, the metadata category having been created with the previous beta. The heading for the custom metadata category that was created, then deleted, remains but no longer offers the metadata name. The orphaned check boxes can actually be checked. There seems to be no other problems associated with the visual presentation.
Turns out that the blank metadata category, which now shows no name, was checked. Unchecking that category removed the check box display from the outline view. While the category (now with no name) remains in the list of metadata list, re-checking that category does not return the check boxes to the outline display.