Thanks for contacting Syncfusion support.
The solution given in the previous updates of this forum is applicable in GridGroupingControl which is an ASP.NET Classic component,but you are using the Essential JS1 (ASP.NET WebForms) component. So, the same cannot be achieved in the Syncfusion Essential JS 1 Asp.Net Webforms.
So kindly share the exact scenario and details regarding your requirement. We will provide the appropriate solution for your requirement.