By serendipitous circumstances I answered a question very similar to this recently to which I will refer You for a detailed look at how the mechanism I am going to propose works:
I believe this is very close to what You are requesting.
The main concept is we need an alternate (new) timeline NOT the "Main Timeline" to be able to jump to a given point in the scene.
I did quick adjustment to the Hype doc You provided. This adjustment only covers a precise set of circumstances but it should to point the way to adjust the rest your project (assuming it is what You actually need of course!): chapters demo_JHSv1.hype.zip (525.6 KB)
Overview
I focused on working with the "Chapter Two" scene as our target chapter - so on the "Home" scene we will click the "Collective Impact by the Numbers" graphic which takes us to "Chapter Two". Clicking on the "Back" button returns us to the same spot in the timeline scroll in the "Home" scene.
Details
The following assumes You have read the post I linked to above.
All the "Main Timeline" references in your functions are changed to a new timeline "Home Timeline". All properties on the Home Scene's "Main Timeline" are removed and transferred to this new "Home Timeline". The only function in the "Scene Load" action for the "Home" scene is "TimelineScroll". There are no "Scene UnLoad" actions.
The "Mouse Click" on the "Collective Impact by the Numbers" graphic now only has the "Jump to Scene" action (to "Chapter Two").
There is a Custom Behavior added to the "Home" scene ("Scene Inspector") called "returnTimeChap2"... it goes to the 4 second mark in the "HomeTimeline" when called. You can of course adjust this time as needed.
"Chapter 2" scene
The "Back" button "Mouse Click" triggers the "Jump to Scene" ("Home" scene) AND the "Custom Behavior" "returnTimeChap2" which takes us to the 4 second mark of the "Home Timeline".