How to add a button to an existing related list in sigma

How to add a button to an existing related list in sigma

There is an existing relationship between Deals and Quotes that is built into zoho crm. We have made a button in sigma that will create a sales order and launch the associated creator app with the id of the new sales order. This is visible from the Quote View. However, I can't see how to do the same for the Quotes related list in Deals.

How do I do this?