I'm on OS 10.14.2 and FIrefox 64.0.2

Hmm. Let's try a test.

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Type about:support in the address bar and press Enter. Under the main banner, press the button; Copy Text To Clipboard.. Now in the Reply Box on the forum page, do a right-click in the box and select Paste.

This will show us your system details. No Personal Information Is Collected.

Fred,

Good suggestion, however I think I found the source. I had turned an app called "Cookie" ON. It is a utility app for managing all forms of cookies, especially tracking cookies. It keeps a "white" list of sites where I allow their cookies. It auto-deletes cookies from sites I do not allow. As soon as I turned "Cookie" OFF, the disappearing bookmarks and history behavior immediately stopped.

My conclusion, so far, is that Cookie conflicts with Firefox's internal cookie managing preference feature.

That was very good work. Well done. Please flag your last post as Solved Problem so others will know.

Contact its support. Bookmarks and history are not stored in any cookies, They are stored in a file called places.sqlite

Back up and restore information in Firefox profiles.{web link} I use an add-on that makes backups of my user profile, Just In Case. Unfortunately, it is not compatible with the current Firefox.

Every now and then, open the profile folder and create a copy of the current profile as is to another location on your hard drive. This way you will have a backup.

If you do this each day, you will not lose much data. This should be done with Firefox Closed.

Note: In case you need to restore from these backups, you may need to overwrite old or corrupted files.