Sorted. I had to create a new function in functions.php:

add_action( 'woocommerce_after_shop_loop_item', 'avia_add_cart_button2', 15);
function avia_add_cart_button2() {
	remove_action( 'woocommerce_after_shop_loop_item', 'avia_add_cart_button', 16);
	...
	...
}

So where in the child theme does config-woocommerce/config.php go? I have tried enfold-child/config-woocommerce/config.php, enfold-child/woocommerce/config-woocommerce/config.php and enfold-child/woocommerce/config.php but the site still refers to enfold/config-woocommerce/config.php. Alternatively how do I edit the “Show details” button as I need to replace it with a dynamic custom dropdown menu.