Moving Tracks between Timelines?

I'm attempting to move Tracks from one Timeline to another. The goal is to merge lots of timelines into a single timeline.

Any idea if this is possible or how to achieve this? I've only just begun with scripting Timeline and Playables so I'm a bit lost. If anyone has an insights I'd greatly appreciate it.

Thanks!

EDIT: I've found both "parent" & "timelineAsset" inside of the TrackAsset class, but they're both read-only. Also tried creating a group track and then using TrackAsset.SetGroup() but it won't let you move between timelines. Not looking good.

EDIT: I found this other thread finally, and ugh, I wish I knew what control tracks were before I went down this road! I'm using control tracks now instead.

*** NEW QUESTION! ***

My control tracks don't seem to work when I create a timeline at runtime. I'm generating a timeline that contains control tracks for several other timelines, but they don't appear to be controlled at all.

If I manually create everything it works. Shouldn't runtime control tracks work? Am I missing something? (I'm also using additive scene loading to jump between different scenes, that could cause issues I suppose)