code: function isColumnReorderable() {
      var originalMethodFromPrototype = Object.getPrototypeOf(this).isColumnReorderable,
          isReorderable = originalMethodFromPrototype.call(this),
          groupedHeaderCellRenderer = this.grid.cellRenderers.get(CLASS_NAME),
          delimiter = groupedHeaderCellRenderer.delimiter;
  
      return (
          isReorderable &&
          !this.columns.find(function(column) { // but only if no grouped columns
              return column.getCellProperty(0, 'renderer') === CLASS_NAME && // header cell using GroupedHeader
                  column.header.indexOf(delimiter) !== -1; // header is part of a group
          })
      );
  }
docs: Prevent column moving when there are any grouped headers.
  @returns {boolean}
  @memberOf groupedHeader
  @inner