When you start typing in Firefox's Location bar, a drop-down list of pages from your history and bookmarks that match what you've typed will be shown. For more information on the autocomplete feature of the Location bar, also known as the "Awesome Bar", see the Address bar autocomplete suggestions in Firefox article.

Why clearing history does not clear the Location bar

Items that appear with a star along the right edge are part of your bookmarks and not your browsing history.

Removing bookmarks results from the list

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Select the Privacy panel.
   
   
3. Beside When using the location bar, suggest, set the drop-down menu to either History or Nothing.
   • History will make the Location bar autocomplete list only display results found in your browsing history, not bookmarks.
   • Nothing will turn off autocomplete.
4. Close the Settings page. Any changes you've made will automatically be saved. .