code: def _on_press(self, event):
          
          if tk.DISABLED in self.state():
              return
  
          region = self.identify_region(event.x, event.y)
  
          if self._drag_cols and region == 'heading':
              self._start_drag_col(event)
          elif self._drag_rows and region == 'cell':
              self._start_drag_row(event)
docs: Start dragging column/row on left click.