How to customize the height of the CaptionSummaryRow in WPF DataGrid (SfDataGrid)?
WPF DataGrid (SfDataGrid) provides support to customize the height of the CaptionSummaryRow by setting the height of the caption summary row in SfDataGrid.QueryRowHeight event.
C#
using Syncfusion.UI.Xaml.Grid.Helpers;
private void DataGrid_QueryRowHeight(object sender, Syncfusion.UI.Xaml.Grid.QueryRowHeightEventArgs e)
{
var rowData = this.dataGrid.GetRecordEntryAtRowIndex(e.RowIndex);
if (rowData == null)
return;
if (rowData.IsGroups)
{
e.Height = 50;
e.Handled = true;
}
}

Take a moment to peruse the documentation, where you can find about row height customization in SfDataGrid, with code examples.
You can download the example from GitHub