Draw a customized line on a Timeline chart

I’m working on a vaadin project involing a Timeline chart.

I wanted to add a horizontal line on the timeline to denote a threshold, and make it thicker than the gridlines to make it noticeable. I also wanted to add a bit of text either just above the line or have it appear on mouse over to explain what the threshhold is.

How do I draw a horizontal line at a specific elevation with a certain width and a text descriptions on a Timeline?


I was wondering if you finally found an answer to this question. I have to show the same kind of information and did not find a way of doing this quickly so far.