Did you try to search for a bookmark you know is in one of the lost folders in case you misplaced the folder (you can't search for a folder name) ?

If you notice you lost bookmarks or accidentally deleted bookmark(s) and you haven't closed Firefox yet then you can use "Organize -> Undo" in the bookmarks manager (Bookmarks -> Show All Bookmarks) to undo this action and restore bookmark(s) you deleted accidentally or otherwise lost/misplaced. You may have to use Undo more than once (Firefox keeps a full undo stack of changes to bookmarks for the current session). Otherwise you can consider to restore the bookmarks from a JSON backup in the bookmarkbackups folder.

• Bookmarks -> Show All Bookmarks -> Import & Backup -> Restore

This will replace all current bookmarks and you lose bookmarks that were added since that backup was created, so you may want to create an HTML backup beforehand and import this backup afterward.

The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once. You also see this count in the Restore menu drop-down list.

• bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4.

See also:

• https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

I got a JSON backup folder from the day I lost my original folders, but it's all code and hieroglyphics. How do I use that to get the mssing items back in my Bookmarks?

You can check the file with this tool to see if it has the lost folders.

• https://www.jeffersonscher.com/res/bookbackreader.html

Note that restoring a JSON backup replace all current bookmarks with the ones in the backup, so you lose newer bookmarks that aren't in the backup.

• https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them