Did the above coding change advised by @LamQSolutions and @SetuBridge_1 work for you? If so, be sure to mark their post as a solution to inform others that may view the thread.
This is a great question! In order to add a custom button to your online store it will require a manual change of coding as this change is not available using the Theme Editor. Since the Dawn theme is designed and supported by Shopify, we can use free design time for Shopify themes to allow our internal teams to make the changes on your behalf.
If you are interested in using the design time, you will need to login to your store using our Contact Us page. This will allow us to securely verify you as the store owner before speaking directly with a Support Advisor about the changes you would like to see.
I can build this feature, where I can add a contact form on the below product specific to the collection or the best would be to have metafield in the product.