Hello all, 

I am using odoo online SaaS. We make monthly a one single invoice (to each customer) coming from multiple sales orders. I want to add in each invoice line the related sales order number. I've tried to do this with studio app but no chance. 

As far as I know I have to edit models or create a new one with many2many relation but my knowledge is not high so will appreciate if you can specify all the steps. 

Thank you a lot in advance