[dbg31415]

I just went through this list and tried everything that worked across Chrome, Firefox, and IE on MacOS and Windows.

* XMarks Alternatives and Similar Software - AlternativeTo.net || https://alternativeto.net/software/xmarks/

So... Bookmark OS, Everysync, xBrowserSync.

And I have to agree, Bookmark OS was the winner. It's not free, but it's only $12 / year. (XMarks being free was probably not good for anyone in the end.)

* Bookmark OS | bookmark manager and organizer || https://bookmarkos.com/