This is a very simple feature which shows a button that has the ability to instantly send the visitor to the Checkout, to purchase a product.
The settings can be located at Settings › WooCommerce › Product Page › Summary Components › Buy Now Button eg: screenshot .
A quick demo can be viewed in this video .
If you want to control on which types of products to show the button, here’s an easy php code snippet you could use below .
add_filter('reycore/module/buy_now', function( $settings ){
$settings['exclude_product_types'] = [
'external',
'grouped',
];
return $settings;
});