How to display the associated products in the product card?

You can add the "See also" section in the block with the catalog products and activate displaying associated products in it that will then be shown when the product details' card is opened.

To activate the section, you need to connect the products from the catalog in the Content of your block, then go to the Settings tab of the block → See also section → choose the category you would like to offer products from → select the number of products in the element and the section's title → save the changes.