You can create node rows using the C1.Win.C1FlexGrid.C1FlexGridBase.Subtotal(C1.Win.C1FlexGrid.AggregateEnum,System.Int32,System.Int32,System.Int32,System.Int32,System.String,C1.Win.C1FlexGrid.AggregateFlags,C1.Win.C1FlexGrid.RowColFlags) method or by setting the Row.IsNode property to true.