Go into Customize mode and drag "Bookmark toolbar items" into the bookmarks toolbar. Alternatively, click the "Restore Defaults" button in the bottom-right corner.

I had gone in there. I did not find customize at first, but did locate it. That area where the folders were supposed to be, showed to me that they were 'still' supposed to be there. I did not think to include a screenshot of that.

Though before reporting, opening and closing private and regular browser windows, all remained empty. After, and I mean right after submitting....the next private browser window opened and all the folders were present. I didn't report that, in hopes to understand "WHY" that occurred & how to rectify if ever happened again (never seen this issue before).