Custom Photos albums within folders are gone after Sierra update
Prior to upgrading to Sierra I had created many albums for specific events (File > New Album...) within Photos, and placed them within folders (File > New Folder). After the upgrade, all of those folders and albums are now gone from the sidebar, however when I use the Search box I can find them and view the associated pictures. Without having to try and recall the names of all of those albums, is there a way to restore the folders and albums to the navigation pane on the left?
iMac with Retina 5K display, macOS Sierra (10.12)