In Firefox, export your bookmarks into html. ...
Bookmarks, Show all Bookmarks, Import and backup, export bookmarks to html.
Then let Brave import that exported html file.
BTW, this is a good way to back up your bookmarks against the possibility of some catastrophic failure. My bookmarks file is about 20 years old. I've been pretty religious about backing it up, and have migrated it from one computer to another for years. I got into the habit way back when Netscape would occasionally get flaky and corrupt the bookmarks. This served me extremely well during the .1 and .2 releases of what eventually became firefox, where it wasn't all that terribly uncommon for something to wipe your bookmarks out during an update. I still have the very first site I ever bookmarked. Sadly it has been defunct for a long time.
Thanks, I’ll see if I can manage to do that. I’ve usually found trying to save email address books to be an exercise in frustration, maybe browser bookmarks will be easier.