I think you can “fake” it. The part I think is the hardest is the beginning. Where it goes from position Auto to position Fixed. But having the side fixed and layered with div’s showing depending on where you are on the site I would think is possible. Using interactions and scroll trigger.
This webflow workshop should help you with the background Transitions scrolling. All of the transitions can be achieved with Webflow I think. Just a matter of breaking it down and seeing what is actually being accomplished.
Please share when you finish. That is how we all learn how to use webflow better.