Option to minimise the period lines
Period lines show the duration of the event. This feature would allow you to show/hide all of the period lines (useful for a timeline where the duration of each event is not so important).
When the period lines are set to hidden, the currently selected event and any starred events would still keep their period lines - this would allow you to pick out a few particular events that have a visible duration, while leaving all other events with hidden period lines.
The setting chosen by the user would also be saved and shared with their timeline.