Ok, sorry to be a further pain. So the position parameter sort of helped, let me just explain what I'm trying to do (I've also updated the codepen to illustrate the problem):
I have the main timeline `parentTimeline` and I want the child timelines (in this case `childTimeline1`) to run in parallel once they've been activated by the parent timeline, so:
parentTimeline: 0-----1-----2-----N-----...
childTimeline1: \0-----1-----2-----N-----....
So essentially the child timelines have a duration of 0 and are only triggered by the parent timeline, but the parent timeline doesn't wait for them. I hope that makes sense.