// Report was obtained before...
// Report report = ...

report.Open(false, false);

// Add a wire harness as a report source.
report.AddReportSources(report.GetAllWireHarnessInfos().Where(s => s.Name == "harness_00001"));

// Add a cable unit as a report source.
report.AddReportSources(report.GetAllCableUnitInfos().Where(s => s.Name == "Cable unit:1"));

// Add both - wire harness and cable unit.
List<DerivationSource> desiredSources = new List<DerivationSource>();
desiredSources.AddRange(report.GetAllWireHarnessInfos().Where(s => s.Name == "harness_00001"));
desiredSources.AddRange(report.GetAllCableUnitInfos().Where(s => s.Name == "Cable unit:1"));

report.AddReportSources(desiredSources);

// Save and close this report.
report.Save();
report.Close();