I got something similar after a Firefox update. You can get them back by re-selecting the correct profile.
I don’t remember exactly how but Internet should be able to help you there
Waterfox user here with no problems: All I can think of is that someone with access to your account (like maybe a family member while you were logged in) accidentally or purposely deleted them.
Sorry that happened to you. Change your password and make a backup next time!
I follow all the best Security practices on my accounts, there's only one account that I logged in from a remote location, and I also can see who goes near that place because I have a surveillance camera directly facing the door... And from my Mozilla account I can see the last time someone used that account...
I did enable Offline Backups, they suck... But hey... They saved me...
Read my other comments to see what's really troubles me... It's weird to lose Bookmarks in such a mysterious way...
Edit: Just checked and my work bookmarks appear to be all there. I did a fresh backup through the Library tool just in case. Hope you get your issue sorted.
I tried searching for anyone else with this issue a month and a half ago, because this happened to me. The bookmarks I lost were not all nested, and I've notice this happen in windows 11 (all exploit protection disabled), and debian 12(both OS different browser profile) I wondered if maybe using the 'Exit' in menu instead of X/middle click tab to close might be related, but I don't know any code evidence in recent releases to corroborate this. This issue was first recognized for me about 2-3 firefox versions ago.
32gb ram i9 9th gen, I use privacy badger, privacy possum, adguard with most filters enabled, decentraleyes, and user agent switcher. I always run in private browsing. I don't think this is related to a malicious website.
I do not have any sync agents like firefox sync enabled. One instance has about 50~ bookmarks with 3 folders no subfolders, one instance has about 500 with many subfolders.
I assume only recently added bookmarks have disappeared, but I have no way to verify and my memory wasn't perfect.
AdGuard/uBlock aren't very different from each other. I've used AdGuard for a long long time, and the browser plugin isn't their only tool I'm familiar with.
If I need better isolation between active sessions, I either end my current session or hop in a VM. Firefox containers are far from perfect and not sure why it was mentioned.
Last time I did my tests, Strict + PP + PB altogether had my preferred outcome on modified/blocked data. Resist fingerprinting did not touch everything I wanted either.
I use UAS to access sites made for other platforms, not to avoid tracking
Decentraleyes: CDN's are not that simple. I have heard there is a better addon for this now though
I add/delete/modify multiple bookmarks a day, and noticed when i use menu-quit it hasn't happened since. Many applications used to clean up differently this way, so I'm not sure. But I do know memory management on different platforms is becoming more and more of a nightmare to track/utilize changes
You don't need to be familiar with git. Just open your browser and visit https://bugzilla.mozilla.org/enter_bug.cgi? create an account on bugzilla and file the bug against Firefox.