Have you read this support article?
https://support.mozilla.org/en-US/kb/sort-bookmarks-quickly-find-ones-you-want

See also:

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

A comment said this did not work on FF 24.0

Yes, won't do what I need.

You can try to use manual sorting as posted by its developer in an answer to a review:

By "manual sorting", I mean using the manual sorting of my extension, not the one from the browser. You can use it via the menu item "Sort Bookmarks" you can see in one the the bookmarks menu beneath the "Show all bookmarks" menu item (the one with the same icon as this extension, not the one in the context menu). Please try this manual sorting to see if it works when the auto sorting does not work anymore (and look at the error console after using this sorting to see relevant errors).

Thats what I'm trying to avoid. Looks like there is no way with the add-on not working.

Without using an extension (if that would work) your only option is to sort each folder manually via the right-click context menu.

Do you know if the extension earlier really doesn't work as a comment about it indicated for FF 24.0?

No, I have never used this extension as I always sort bookmarks manually and would never sort them automatically or otherwise.

If the extension isn't working in Firefox 24 (the comments aren't clear about this) then you can try to contact its developer.

Thanks

(deleted)

What?

Sorry, something went wrong with that reply, so please ignore.