Hello! You can delete separators by going to Bookmarks>Show all Bookmarks (or pressing ctrl shift b) to open the bookmarks library. Go to the folder you are having an issue with and select the separators you would like to delete. Delete them by pressing the Delete key or right clicking them and clicking the option Delete. You can hide the bookmark bar by right clicking where the top bar where your tabs are (see screenshot for details) and de-selecting the Bookmarks Toolbar option.

Have a great day!!

Jon

See also:

• https://support.mozilla.org/kb/how-do-i-delete-bookmark

Bookmarks and separators on the Bookmarks Toolbar are in the Bookmarks Toolbar folder, so open that folder to remove the separator(s) via the Organize menu.