@nito What I am talking about is not smooth scrolling of the preferences. I have noticed the existence now. When I install Vivaldi, I recommend installing the application to macOS by Vivaldi. I think that it is an add-on attached to it.

Correction: Swipe navigation works intermittently in Vivaldi 1.6 RC!

It was working fine then it suddenly stopped working! If I open a page in a new window and click some links to generate history, it starts working again.

I've reported the issue and hopefully they can get this working reliably again soon.