These instructions will combine the new bookmarks with the old.

Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B.

Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Export Bookmarks To HTML, and follow the prompts and save it to a HTML file. Copy the file to another computer/profile. Repeat the instructions above, BUT select Import Bookmarks From HTML.

https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them

https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

In addition to the keyboard shortcut, if you use the Bookmarks menu on the classic menu bar, it should have "Show All Bookmarks" which is the way to call up the Library.

Also, I think FredMcD probably meant to include these articles if you prefer the HTML format:

• Export Firefox bookmarks to an HTML file to back up or transfer bookmarks
• Import Bookmarks from an HTML file

Thank You. The FireFox help link was difficult for me to follow. This solved it for me.

Glad to help. Safe Surfing.