Hi Richard,
Sorry for the delay.
The Frozen columns of the GridGroupingControl will be freezed and will be unable to move through dragging. Instead you can apply the frozen column to Grouping through the code.
Please refer the code below:
this.gridGroupingControl1.TableDescriptor.GroupedColumns.Add("parentID");
Also refer the sample attached below:
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=GGCBehavior-284216130.zipLet me know if you have any queries.
Regards,
Nirmal