Which Polaris Components make up the Immersive Editor page layout?

[rheannonedev]

This page shows an "Immersive Editor" specialty screen type. 
Which Polaris Components are combined to make this screen type? 
I can see the top bar navigation with a dropdown of page templates but the "Preview" looks native. 

Which Polaris component would be used for this kind of page template preview? 
https://polaris.shopify.com/patterns/page-layouts#specialty-screen-types