Here’s a short and handy tutorial about the Siteorigin PageBuilder. In Pagebuilder each row will get an id. Then each row will get an id in the Pagebuilder settings.

Now the video does not tell this, but I guess that Pagebuilder will set bookmarks on the webpage, as in:

<h2 id="row-about-us">About us ...</h2>

In the WordPress menu the internal links will be used. The menu will link to #row-about-us, and Pagebuilder will create markup somewhat like in this sample:

<a href="#row-about-us">About us</a>

Now onepagers tend to scroll in a cool slow way. You can do this via some JavaScript. I guess there’s a plugin for it too.