The timeline shows a blue strip along the top that corresponds with all animations that exist within the timeline.
Consider a group in the timeline that contains animated child elements.
When the group is expanded, the children’s keys are visible on the timeline
But when group is closed, no keys are visible.
This can be an issue when trying to find an animated element in the scene. We know it’s there somewhere but you have to open all closed groups to find it.
when group is closed, blue strip(s) on timeline (on the group’s line) indicate that it contains animated children.
(This would also make it consistent with 3D animation packages too)