More: I've now tried the "Moving bookmarks to another computer" -> "using bookmark backup file" instructions posted at https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them#w_restoring-from-backups . This time I used a Windows PC bookmark backup file from last week, and not a new export. The results were the same as I reported above: All 5K or so bookmarks end up at the top level of my Linux PC bookmarks, and not in their original folders.

What file format are you using? Sometimes the json files become corrupted.

http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

jscher2000 has a tool on his website to extract out your bookmarks and save them to an HTML-format bookmark export file. If you want to try it, here is the page:

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

To open the bookmarkbackups folder in Finder, use the "Open in Finder" button in the first table on the Troubleshooting Information page, and double-click into bookmarkbackups where you should see several dated files. From there you can drag and drop onto the conversion tool.

To import the HTML file, see the steps in this article: Import Bookmarks from an HTML file.

Thank you, Fred.

I'll take a look at those references.

Is "file format" filetype? If so, the bookmark exports I create manually are filetype .json, and the ones from my bookmarkbackups folder are filetype .jsonlz4.

Thanks again, RL

As I said above;

Sometimes the json files become corrupted.

This is how I do a backup.

These instructions will combine the new bookmarks with the old.

Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B. Firefox 84+ <Control> (Mac=<Command>) <Shift> O.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Export Bookmarks To HTML, and follow the prompts and save it to a HTML file. Copy the file to another computer/profile. Repeat the instructions above, BUT select Import Bookmarks From HTML.

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

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

Mozilla search: Import {web link}

If you run the extension Default Bookmark Folder on any of your installations of Firefox, make sure it is NOT enabled during import or restore. If it is enabled, it dutifully moves every bookmark to your default folder, which is not what you want during those operations.

jscher2000, thank you, that was indeed the problem.

I don't know why it finally hit me now on my linux system, and not the windows systems, but after I disabled the extension I was able to restore the bookmarks correctly.

Thanks again, RL