I have created a modified version that I believe is what You are looking for. However, I am out of time to buff things out and do a write-up about it. There are some contrary things on the timelines in your original version that I’ve simply eliminated…
Example: The “Scene Load” on Scene 2 has an action that goes to the 4 second mark in the “Main Timeline” and will override any of our attempts to go to six seconds (“Book Cover 4”) with a Custom Behavior. I’ve tried to accommodate this situation but I couldn’t in the time I have allotted to this project - so I removed that action.
My version is not an attempt to re-create what You are doing but rather to show how to do a Scene Transition and go to a particular location in the desired timeline. I might have time to finish up tomorrow.
In the meantime I have created a screen recording that shows the idea.
Before I start work on your project again I will check in tomorrow to see if You think the general concept of my version is going in the right direction. Again, do not worry about interface details - just if the transition works the way You are envisioning.
The key element here is we are NOT going to use the “Main Timeline” for these scene transitions, we will use an alternate (new) timeline in “Scene 1” called “Slider”. This alternate timeline is critical to having things work as we want them to work.
Drag the “Scrubber” on the left side up or down to view the different book rows. The scrubber controls the “Slider” timeline (via “On Drag” in the “Action Inspector”). This “Slider” timeline is the key to going to the correct row when we return to “Scene 1” from the book content scenes (i.e. for Books 1, 4, & 7).
Books 1, 4, & 7 are set up for mouse clicks. A click triggers a “Push Bottom to Top” scene transition and goes to the corresponding scene (“Book Content~Pages”) for that book.
There is a “Back Arrow” on these “Book Content” scenes that takes the viewer back to “Scene 1”. This “Mouse Click” trigger runs a scene transition (“Push Top to Bottom”) AND runs a Custom Behavior matched to the corresponding book row (via Scene 1’s “Slider” timeline)… e.g. going back to “Scene 1” from the “Book 7” content scene we trigger the Custom Behavior “timeBook7”.