This sample shows how to use the Save and Load events in the code. You can add the event listeners to the StiOptions.Engine.GlobalEvents at application initialization:
public Window1()
{
	StiOptions.Wpf.CurrentTheme = StiOptions.Wpf.Themes.Office2013Theme;
	InitializeComponent();
	
	StiOptions.Engine.GlobalEvents.SavingReportInDesigner += 
		new Stimulsoft.Report.Design.StiSavingObjectEventHandler(GlobalEvents_SavingReportInDesigner);
	StiOptions.Engine.GlobalEvents.LoadingReportInDesigner += 
		new Stimulsoft.Report.Design.StiLoadingObjectEventHandler(GlobalEvents_LoadingReportInDesigner);
}

Then specify the action to be performed when the report is loading:
private void GlobalEvents_LoadingReportInDesigner(object sender, Stimulsoft.Report.Design.StiLoadingObjectEventArgs e)
{
	e.Processed = true;
	
	StiReport report = new StiReport();
	report.Load("..\\SimpleList.mrt");
	designerControl1.Report = report;
}

Specify the action to be performed when the report is saving:
private void GlobalEvents_SavingReportInDesigner(object sender, Stimulsoft.Report.Design.StiSavingObjectEventArgs e)
{
	if (designerControl1.Report == null) return;
	e.Processed = true;
	
	designerControl1.Report.Save("Report.mrt");
}

На скриншоте ниже Вы можете увидеть результат выполнения данного кода:

Save and Load events of the Designer