I updated the chapter versions above … no more custom behavior listener to determine current chapter. I was thinking maybe always adding a default chapter marker at the beginning and end of a timeline would be a nice idea (in the lookup, that is). Food for thought.
I did not remove custom behavior as a way to set them, just the listener to determine the last chapter. Now, it is simply fetched by comparing the current time to the lookup.
BTW, having the chapter marker be custom behavior has a pleasant upside, you can just react to the play head passing a chapter by setting up an action stack that triggers in such cases (scene panel).