Hi Thomas Ellingsen,
Thank you for contacting Syncfusion Support.
In SfDataGrid does not contain the direct support to achieve your requirement “show Header text above and checkbox under the text in a column header”. Currently we are checking possibilities to achieve your requirement via workaround. So, we need two more business days to validate this. We will update with further details on or before November 29, 2021.
We appreciate your patience and understanding.
Regards,
Vijayarasan S