The only thing I can think of is (if there aren't a million of them) click on each Firefox b/m and hit command-D to create a new one in Safari.
It seems like there ought to be an easy way to do it, or maybe we're misinterpreting "import" and giving it more import than it deserves.
Not quite a million, but unfortunately there are several hundred bookmarks. So that's a non-starter.
I'll just leave things as is; it's sufficient for my purposes.
Again, many thanks.
