The product photo displayed on the collection page of the Shopify theme Dawn is fixed to the first image registered in the product information (second image when the mouse is over), but here is how to set it so that you can specify an image of your choice. There is an input field in the meta field, so you can specify it for each product.
How to set up the Dawn theme so that you can specify images other than the first and second images for the product thumbnails in the collection
Setup Step 1: Create product metafields
Step 2: Modify card-product.liquid (Part 1: Main thumbnail image)
Step 3: Modify card-product.liquid (Part 2: Thumbnail image when hovering mouse over)
