Y-Axis in Evolution Graph

Hi! I’m trying to display an evolution graph with a metric created by me. The problem is that I want to show the metric’s range in a new Y-Axis. I can see that metrics like Bounce Rate, Avg. Visit Duration, Avg. Generation time, among others, make the graph to display a second Y-Axis. How can achieve this for my new metric? Right now I can make it work but using the normal Y-Axis.

Thank you very much.