Cannot delete Unassigned Items

I recently deleted most of my Notebook contents (very laborious and time-consuming). There are 35 Unassigned Items remaining and I cannot see them nor delete them. On LDS.org, under Study Tools, it indicates that these items are Highlights. How can I see these, or delete them?

If you go to the Notes section of the app, under All, you'll see all of your annotations, and you can delete them.