The Library offers options to sort folders in the same way it sorts the bookmarks.

You will need to look at a folder with subfolders, to see this happen. The bookmarks menu itself is one such folder. The sorting is temporary.

You may also drag and drop folders to rearrange their order. (IIRC they retain the sort order if they are sorted then copied and pasted)

I suggest you backup the bookmarks first if you plan major changes.

• see back up your bookmarks or move them to another computer

Thanks, John99.

I was able to sort the folders alphabetically using the Library view. Unfortunately, changing the order of folders in "Library" has no impact on how the folders are ordered in the sidebar. How strange! Since the sidebar is much more convenient to access, I still need a way to sort the folders it displays.

Do your changes in the Bookmarks Sidebar to make it permanent.

https://support.mozilla.org/en-US/kb/sort-bookmarks-quickly-find-ones-you-want

If you decide to Sort by Name, the sorting will be within Separators (the dotted line). You can have alpha-sorted bookmarks along with manually sorted bookmarks and folders by using the separators to separate the "different types of sorts".

Don't use the Views menu to sort as that is only for viewing bookmarks in the bookmarks manager (hence the name of the menu item).
To sort items you need to use Sort By Name in the right-click context menu in the right pane.

• http://kb.mozillazine.org/Sorting_and_rearranging_bookmarks_-_Firefox