Hi,
Hope everything is going well.
This issue seems to be more related to the bookmark function of Firefox browser. Here are some helpful articles for your reference:
I've lost all bookmarks, saved passwords etc. after an update, please help
https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks
(Please Note: Since the website is not hosted by Microsoft, just for your reference.)
Feel free to contact me if you have any concerns/queries.
Best regards,
Simon
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