We got this question from many of our customers. That's why we created an add on called Flexible BoM. See: Odoo Flexible BoM

Hi Paul, May i know the purpose of BOM in quotes?

Hello , Do you found solution ?

Hi Paul,

There is no such feature available by default. You can add a custom Many2one field with the relation of mrp.bom model. Using that field you can add/create the bom. 

Otherwise, you can add that field in orderline which directly picks the bom of the product 

Try the following 

Class SaleOrderLine(models.Model):

​_inherit = 'sale.order.line'

bom_id = fields.Many2one("mrp.bom", related='product_id.bom_id', string="Bill Of Material")

Regards