missing some bookmarks
I reinstalled Win10, clean install. Reinstalled Firefox, v88 and imported my bookmarks (.json). Took a while (36.4Mo) but they got imported and I got to sort the latest bookmarks them into folders and tags while I transferred files from a hard drive. Trimmed them to 31 Mo and saved a backup. Exited firefox. Later I launch firefox to install addons and notice all my latest bookmarks have vanished. All my tags are gone too.
When I check to restore my backup, I have the choice between - today's automated backup (11 Mo; 110.000 items) 100.000 items, that is, half of my bookmarks. - ... or my manual save I did. Restoring my manual save returns the bookmarks and tags. But they disappear when I exit firefox. Sitting for half a hour for my bookmarks to load each time I launch firefox is not a solution. I estimate there's 70k to 100k links and 1k tags missing.
I have one only profile. Fresh, latest FF, no addons. No clue too.
Opaite Mbohovái (2)
As I understand you, there is an old profile somewhere. You can recover bookmarks from it by copying, with Firefox closed and after renaming the new equivalents, the files places.sqlite and favicons.sqlite: https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile I haven't looked at these articles but they are linked in the margin: https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them
Is your Firefox connected to a Firefox Account? If so, you may want to disable bookmark sync temporarily until the situation stabilizes.