Hi Bruno ,
Below are the forum thread that discusses about the drag & drop of rows in GridGroupingControl and let me know if this helps.
http://www.syncfusion.com/Support/Forums/message.aspx?MessageID=49136Also refer these KB article for more details.
http://www.syncfusion.com/support/kb/grid/Default.aspx?ToDo=view&questId=235Regards,
Nagaraj