Check this firefox community support page: https://support.mozilla.org/en-US/kb/cant-add-change-or-save-bookmarks

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address bar.

You will find Places Database near the bottom. Press the Verify Integrity button.

When done, copy and post the results here.

Note that you seem to be working a special funnelcake 86 Firefox version (updateChannel: release-cck-mozilla86), so you may want to do a clean reinstall.

You can find the full version of the current Firefox release (63.0.1) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/
• https://www.mozilla.org/en-US/firefox/63.0.1/releasenotes/

Funnelcake builds are an experiment offered as a special Firefox version to (new) users for testing the user experience.

If you use Sync then best is to disconnect Sync temporarily during troubleshooting.

If "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page cannot repair places.sqlite then remove all places.sqlite files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created

See also:

• https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox