Visualize the difference between Metrics by Dimension Series in Line Chart

What is the problem or goal the end user is trying to solve or accomplish?

the customer is looking to visualize the difference between metrics for the different dimensions he has instead of visualizaing the values of metrics themselves

How are they solving it currently?

a way to do that would be to create calculated columns but this is not feasible to scale when there are a lot of different dimensions

What is the recommended solution by the Customer?

customer would like to be able to define a base dimension metric, and display the metrics of all other dimensions metric not as the actual value but the difference between this dimension metric and the base dimension metric