Hi Franz,
You have to use ApplyXmlLookAndFeel(..) function for reapplying the saved state. The LookAndFeel refers to property settings in the GridGroupingControl such as whether the AddNewRow is below or above the records, color properties, etc.
I have a sample prepared for demonstrating this. Please download it from the following link,
http://websamples.syncfusion.com/samples/Grid.Windows/F68447/main.htmPlease let me know if this helps you out.
Thanks,
Fahad