Sayers London review for Google & YouTube

I'd love to use this app, but like most stores, my product ids in Google Shopping are not Shopify product ids - they existed before they were on Shopify. Without being able to choose which field acts as the item id, this app is useless. Even if you don't use the Google Shopping features, it will not record conversions correctly either because the product ids will be different. I can't change the product ids in Google Shopping, as then I'll lose years of data on those items. Simple fix would make this app great