MarysMac Said:
"Safari bookmark folder disappears: The bookmark folder I use most often and that I titled "Bank and Health" keeps disappearing from my "Favorites." I know how to restore it using Time Machine, but I would prefer not to have to go through that exercise every time it disappears. I have replaced the Bookmarks.plist a dozen time, but the disappearing act keeps happening."
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Have you Reinstalled the MacOS Yet?:
If this is continuous, then perhaps there is a kernel corrupted, somewhere within the system files -- something particularly related to Safari.
So, rather than restore Safari from Time Machine, reinstall the macOS. Nothing would be deleted; it's just that all system files would be configured to how and where they should be.
The intent is to get Safari to load as intended.
Go Here: How to reinstall macOS from macOS Recovery
Use: Command (⌘)-R
Reinstall the latest macOS that was installed on your Mac (recommended).