In reply to Marcus Hiles.

Notably, the way Yoast integrates is via the sidebar API, which creates an icon in the top right which opens a sidebar when clicked. This icon can be unpinned, which will put it in the ellipsis menu on the far right. It kind of works like the extensions in Chrome or the add-ons in Firefox, where you can choose to only show your most used plugin sidebars in the top bar, and leave the rest in the ellipsis menu.

I think it is recommended to use this plugin sidebar API over adding stuff to the normal Document Settings sidebar.

I think this pinning/sidebar system works as a suitable replacement for the old screen options.