My Shopify site already collects shipping details from the customer before checkout, including pick up from store option so it is confusing for the customer when they select to pay using PayPal and get asked by PayPal to confirm or change their shipping address.
I have looked at various solutions and most seem to suggest editing the API code to include:
But I have no idea where to put this code. I am using Vantage Theme.
I've been looking to solve this for hours..
This looks like a change that would be made to how Shopify interacts with PayPal's SDK/API, not a Shopify API specifically. At the moment, this can't be changed, but we can log it internally.