Hi David,
Thanks for posting here.
There is only one Timeline per page, and it's attached to the page itself. Unfortunately you cannot directly add layers to a Timeline. You have a couple workarounds, though:
You can show invisible shapes in the Timeline, and then create actions to say "when Shape 4 is shown, show Layer 4".
Or, you can create Cue Points on the Timeline, and create actions based off those Cues.
Here's a video:
https://share.smartbuilder.com/public/support/control-layers-from-timeline.mp4Hope that helps!
- Nav