I can not believe it as a browser in this category does not have synchronization
This might blow your mind, but you've got to know that a web browser is not something that you can build overnight...
What category would that be?
Remote synchronization needs sync servers. Vivaldi will build up such server structure. And as i might guess Vivaldi will have sync to local destination, over ssh, to own cloud, to ftp etc.
But its is not ready yet.