What problem does this feature solve?

We have a requirement where a user can place multiple tooltips by clicking on a chart. example: If i am trying to see the exact value of a graph at time X and Y simultaneously, right now have to hover back and fro constantly.. if it is a simple map, there may be other ways, but for a complex time based data stream it would be extremely difficult.

so user can hover over and place a tooltip wherever they want, to dismiss , they can either click on the tooltip OR have a close button on the tooltip...

What does the proposed API look like?

tooltip: {
   multiple: true
}