This question talks about showing the values on hoover JavaFX LineChart Hover Values
You can likey adapt that solution to show the values all of the time.
Here is the example code refrenced there https://gist.github.com/jewelsea/4681797
This code is untested but I would start by using the example with this modification
HoveredThresholdNode(int priorValue, int value) {
setPrefSize(15, 15);
final Label label = createDataThresholdLabel(priorValue, value);
getChildren().setAll(label);
toFront();
}
From there you can start to pull away the parts you dont need.