I have set up an area on the Classic Commerce website to start listing useful code snippets for Classic Commerce.
These are small pieces of code that add minor functionality without the need for extra plugins. They can be used in either the functions.php file in a child theme, or in a utility plugin that you have created specifically for that purpose.
The idea is similar to the one currently available on the WooCommerce docs…
If you have a code snippet that you find useful in CC/WC then post it here and I will add it. Please include a sentence or two about what the snippet does and why it is useful.