I cannot delete bookmarks.
The "library" button only lists the bookmarks, not a left and right screen. Any clicking on bookmark just tries to open it. There is no delete option which works. I use a Mac desktop.
When you're in the Library (Cmd+Shift+B), at the upper left, you'll see three buttons (unfortunately not labeled on Mac) :
1st button (cog wheel) = "Organize" - when you click on it, you'll get a drop down with options, among which "Delete". Highlight the bookmark you want to delete, then click that button.
2nd button = "Views", 3d button = "Import and Backup".