The order of columns display is defined by the table col_order attribute. The value of this attribute is the comma separated list of columns IDs. The order of columns IDs in this list defines the order of their display. So, to change columns order one should change the order of columns listed in the col_order attribute.
Note: If the col_order attribute is absent, columns are displayed as defined in the table columns attribute. The columns attribute value must NOT be changed.