By default, the items displayed on the Timeline are unordered. They are stacked in the order that they where loaded. This means that way items are stacked can change while moving and zooming the Timeline.
To display and stack the items in a controlled order, you can provide a
custom sorting function via the configuration option order.
WARNING: Custom ordering is only suitable for small amounts of items (up to a few hundred), as the Timeline has to render all items once on load to determine their width and height.