I do not use the Bookmarks Bar, I prefer to use the old Menu Bar at the top of the screen :
This has the File,Edit,View, etc drop down menus available all the time.
To display the Menu Bar, right click the three horizontal lines, (Hamburger), and select "Customise Toolbar..."
Then select Toolbars and Menu Bar from the bottom of the screen.
I have accidentally left clicked on the Bookmarks dropdown menu and selected and dropped several bookmark folders into other folders by mistake. Followed by a couple of hours tying to find what was moved and to where, then dragging and dropping them back to their correct locations. an undo/go back button would be a life saver in Firefox...