By selecting two point in the chart, in the same way of the values invalidation, it is possible to add an event to the chart.
By clicking the Add event button, a window is shown, to insert tags and the description.
Once the operation is confirmed, the event is shown in the chart area. When the mouse cursor enters the event area in the chart, a balloon with its detail is shown.
The event created in the chart can also be seen in the notes widget list.