Many themes suggest/require the use of “Child Theme” in order to be able to add custom functions. It replicates functions.php so that when WordPress is updated your custom code doesn’t get overwritten. Well this can be a pain in the ass to set up, but I found a plugin that replicates this using a plugin without having to set up a child theme.

My Custom Functions

Once installed it gives you an area under Settings > PHP Inserter to add to.

In this case I had to set the default value of amount of products displayed in WooCommerce from the default of 12 to ALL. This is a good guide: https://theme.co/apex/forums/topic/how-to-display-all-your-products-in-shop-page/#post-241707

and I used this snippet but changed 24 to 1000:

// Display 24 products per page.
add_filter( ‘loop_shop_per_page’, create_function( ‘$cols’, ‘return 24;’ ), 20 );