XML Side Code

        <field name="order_line"widget="section_and_note_one2many">
            <tree string="Sales Order Lines"editable="bottom">
            <control>
                <create string="Add a product"/>
                <create string="Add a section" context="{'default_display_type': 'line_section'}"/>
                <create string="Add a note" context="{'default_display_type': 'line_note'}"/>

             </control>
            </tree>
        </field>
      

Python Side Code

    display_type = fields.Selection([
      ('line_section', "Section"),
      ('line_note', "Note")], default=False, help="Technical field for UX purpose.")

    @api.model
    def create(self, values):
        if values.get('display_type', self.default_get(['display_type'])['display_type']):
            values.update(product_id=False, price_unit=0, product_uom_qty=0, product_uom=False, customer_lead=0)
        line = super(SaleOrderLine, self).create(values)
        return line

    @api.multi
    def write(self, values):
        if 'display_type' in values and self.filtered(lambda line: line.display_type != values.get('display_type')):
            raise UserError("You cannot change the type of a sale order line. Instead you should delete the current line and create a new line of the proper type.")
        result = super(SaleOrderLine, self).write(values)
        return result