Magento 2 Product Custom Option Preselect extension helps to set the custom option default value for the product. The custom option default value can be visible on the Product Page. Magento 2 Product Custom Option Preselect extension helps you to create a user-friendly interface for your eCommerce store.
Preselected custom option values by default/preselect on the product page. Admin can set default options from the product page. Admin can set first option value preselect, minimum value preselect or maximum value preselect. Set the custom option default value with all types. Supported multiple types of products. Make it the fastest, easiest and user-friendly interface. Supported with GraphQL/REST API
For more detail : Magento 2 Product Custom Option Preselect extension