Backup Vivaldi Profiles: an example
Backup Settings option: This topic is "high on the list" to be added to Vivaldi. An example of this type of software already exists for Mozilla products: MozBackup.
"MozBackup is a tool — a standalone utility — that allows you to backup and restore bookmarks, mail, contacts, history, extensions, passwords, cache etc." [http://mozbackup.jasnapaka.com].
While it is not a "Sync" option, I find useful. Maybe Vivaldi developers could produce something like this. More info is http://kb.mozillazine.org/MozBackup.