Snap Section Side Navigation

I have a number of snap sections setup using some custom CSS. The problem I am having is I can’t get the side Nav links to scroll to the relevant sections and have that highlight which nav section is active.

Here is my site Read-Only: LINK
(how to share your site Read-Only link)

It’s difficult to test out custom code changes because the results of the change are only visible after publishing.

I’ve had success using Scrollify for snapping to sections. You can see how the sections are set up and the custom code on the homepage of this sample site: