A pie chart by definition represents only one set of datapoints. So if you want to see the datapoints that are now hidden in rsm, set up the piechart for showing only the rsm data.
See some demos in https://mydemoversion8-sandbox.mxapps.io/p/charts and/or check that sourcecode for how to set it up.
So the answer to your question: feed the piechart with on set of datapoints, each point having a label and a value