With the extension "Product number in listings" the product number can be added to the product boxes in your category listings.
Note: The product number is shown in the product box if the "Show product number" configuration is enabled and the product has a product number.
Go to the "Listing pages" tab
Expand the "Product box" block
Scroll to the "Content" section
Enable the configuration "Show product number"
Save your changes after editing
Edit the label prefixing the product number using the following snippet:
twt.listing.ordernumberLabel
The product number is automatically added
Tab "Listing pages" => Block "Product box" => Section "Content" => Show product number
twt.listing.ordernumberLabel
Note: For information on how to edit snippets, see the following instructions: Texts: Editing and translation
Tip: If a change does not affect the storefront, just clear the Shopware cache: Clearing / warming up the Shopware cache