Open the Bookmarks Manager. Go to the directory 'tree' and right-click each sub-folder, selecting Sort.

Thanks, but was looking for one click to sort everything, rather than having to crawl through every folder and sort each one indiviually.

Go to the Mozilla Add-ons Web Page {web Link} (There’s a lot of good stuff here) and search for what you want.

Sort Bookmarks https://addons.mozilla.org/firefox/addon/sort-bookmarks-webext/ Bookmarks Organizer https://addons.mozilla.org/firefox/addon/bookmarks-organizer/ Auto-Sort Bookmarks https://addons.mozilla.org/firefox/addon/auto-sort-bookmarks/

Thank you @FredMcD. I found a tool called -wait for it- ... Sort Bookmarks ! Problem solved.