How Do I Resize Columns?
Using the Property Inspector

Select the data grid and open the property inspector. Navigate to the Columns pane (1), select the column you want to modify (2), and set the width of the column using the Width text entry field (3).
Using Script

You can set the size of a column by setting the dgColumnWidth property for the column to an integer.
set the dgColumnWidth["Name"] of group "DataGrid" to 150
How can I resize all the columns of datagrid from code?
With this instruction we can resize one by one
set the dgColumnWidth["Name"] of group "DataGrid" to 150
Thanks!