As far as I can tell, bookmarks accumulate forever... however, it's possible to accidentally drag-and-drop a bookmark or entire folder into another folder and lose track of it.

If you search in the Library dialog (Ctrl+Shift+b) for one of the missing bookmarks, can you find it? The dialog doesn't have a column for folder location, but you can install an extension to add that column:

https://addons.mozilla.org/en-us/firefox/addon/show-parent-folder/

To see the entire folder hierarchy of the found bookmark, you need to switch on an option. You can do that on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, find Show Parent Folder in the list and click its Options button.

Any luck?

Note: Firefox keeps backups for a limited time. If you determine that some bookmarks were deleted recently, it's possible to restore a backup. However, then you would lose bookmarks added since the backup date. You can work around this in multiple steps, but I'll spare you the details unless needed.

You can also check if you haven't moved them (or an entire folder) into another folder by accident, so you do not see them anymore in the expected location.

Thank you so much. You can tell from my username I'm not a techie :-)