To create column charts and pie charts with multiple columns/slices, generate a report with sub-reports using a period (.) to separate the report and sub-report names. For example, if you'd like to create a chart that reports GFA for different types of buildings (e.g., retail, residential, office, hospital, etc.), then, generate reports in CGA with the following names: GFA.Retail, GFA.Residential, GFA.Office, GFA.Hospital, etc.
report("GFA.Retail", geometry.area)
report("GFA.Residential", geometry.area)
Or, if you have the building type in a variable, you can create strings for the report name:
buildingType = "Office"
reportName = "GFA." + buildingType
report(reportName, geometry.area)
More about creating sub-reports can be found in Tutorial 11 in the "Greenspace and BuildUp Area Reports" section: Tutorial 11: Reporting—CityEngine Tutorials | ArcGIS for Desktop
Then, create the dashboard by selecting "GFA" as the "Report".