Stateflow can detect unused data, events, messages, and functions when the corresponding diagnostic is set to 'warning' or 'error'. However, please note that the diagnostic is only performed during a model update of the Stateflow Chart. If a Chart has not changed since a previous model update, the Chart will not be analyzed again, and as such the diagnostics are not shown. Please refer to the following documentation for more information:
It seems that the Stateflow API is not capable of directly removing these unused data or events. The only possible workaround you could try is to first let Simulink detect unused data and events, and then report the diagnostic messages programmatically. Afterwards, you might parse the error messages and remove those accordingly. The following documentation could be helpful:
