Thank you for contacting Syncfusion support.
As of now, we don’t have support for your requirement of “Grid picker column Multi-selection” in Datagrid Xamarin.Forms. We can do the single selection the grid picker column,
Can you please elaborate your requirement in detail along with screen shots (if possible)? How you want this support whether to select the multiple cells in the grid column with use case scenario, it will be helpful for us to check on it and validate your requirement.
Subburaj Pandian V