Ad Hoc only allows us to plot on 1 Y axis. Being able to plot on a 2nd, especially in the case of calculated metrics, would make the visualization much better. See example below. The green line is visits. The blue is a conversion event. The red is the conversion rate. That conversion rate really takes off but you can't see that on the chart below. An option similar to what Excel allows us to do would make this chart much more impactful.