This feature requires the use of Shopify Product Cards component
The developer - Ervinne, is still unsure how it's organically generated, but we may force recommended products with the help of Shopify Search & Discovery app.
Forcing or Viewing Related Products
Go back to this store's admin > apps > Search & Discovery > Recommendations: and set the recommendations you want for your products. Right now we are getting "Related Products" so note that adding "Complementary Products" will have no effect to this product card.
Right now, this store has organically generated related products, for example Catapult Fishing Equipment Kit will show you a Related Products section that's added to to the Product Page in advance.
Setup Instructions
Follow the installation instructions in the README of the Shopify Product Cards Component.
This project has the files copied in advance and you should be able to see the related products of a selected product below. You may also customize which product is displayed here by going to this store's admin and updating the "Article Related Products" section and select the product handle you wish to check.