There's not a blank bar there now -- it's just completely gone? To turn the Bookmarks Toolbar on, you can use one of these methods to show the toolbar list and select the bar there:

• right-click a blank spot on the tab bar (or the "+" button)
• tap the Alt key to activate the classic menu bar > View > Toolbars
• in Customize mode > Show/Hide Toolbars (see: Customize Firefox controls, buttons and toolbars)

To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list.

Does that bring it all back?

Make sure that toolbars like the "Bookmarks Toolbar" are visible.

• "3-bar" menu button > Customize > Show/Hide Toolbars
• View > Toolbars
  You can tap the Alt key or press F10 to show the Menu Bar
• Right-click empty toolbar area

Open the Customize window and set which toolbar items to display.

• "3-bar" menu button > Customize

• check that "Bookmarks Toolbar Items" is on the Bookmarks Toolbar
• if "Bookmarks Toolbar Items" is not on the Bookmarks Toolbar then drag it back from the Customize palette to the Customize window to the Bookmarks Toolbar

• if missing items are in the Customize palette then drag them back from the Customize window to the toolbar
• if you do not see an item on a toolbar and in the Customize palette then click the Restore Defaults button in the Customize palette window to restore the default toolbar set.

• https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars
• https://support.mozilla.org/kb/navigation-buttons-missing

Thank you! That was the one thing I needed that I couldn't remember and could find an answer for in search.