|OS Platform|macOS| 10.13.3
I imported bookmarks from an HTML file, all went well.
I moved them from the “Imported from HTML” folder to the “Other Bookmarks” folder.
I was moving a folder from “Imported” to “Other” and they all had vanished. Note that the Bookmarks Toolbar shows empty, but there are bookmarks across the top of the screen.
When I type one of the known sites imported, it shows as if it were in the bookmarks (e.g. allrecipes … pulled up https://www.allrecipes.com/home)
Restarting Brave didn’t have any effect of this.
Addendum: I tried creating a new folder - it said created but it wasn’t visible.