To edit the Related products, please first make sure you have installed the Search & Discovery app from Shopify.
After that, open the app and navigate to the Recommendations section, then select the product you would like to set up related product for it.
By default, Shopify will automatically generate 10 recommended products for each item. These products are labeled as “auto-generated” and cannot be edited or removed.
However, you can still add additional products manually to customize the recommendations as needed.
Please refer to the provided video: