These two icons in the ‘Shipments’ tab toolbar allow you to switch from standard to compact view. This will impact how the timeline is displayed:
In standard view you will see each of the four main milestone's location and confirmed or adjusted date of completion. The mode of transport icons are also displayed for each segment.
In compact view you will see the routing (departure and arrival locations) on the left of the timeline below the shipment references. The timeline only shows whether a segment has been completed or is in progress of being completed.