Filters

Display WhatsApp button when the product is out of stock

add_filter('njt_wa_out_of_stock_display', '__return_true'); // Add this code to theme functions.php

Display WhatsApp chat widget in custom post types

When you want to display the WhatsApp widget only on specific pages and custom post types, please follow these steps.
Go to the Display Settings tab and select Show on these pages. It will list your published pages and posts as checkboxes. Please select those pages which you want to display the widget on.
Then, please add this snippet to display the WhatsApp widget in custom post types.
add_filter('njt_whatsapp_display_in_post_types', function($post_types){
$post_types = ['movie', 'reviews']; // movie, reviews are custom post type you want to display the widget
return $post_types;
});
Your code snippet may look like this. Please add those CPTs based on your purposes.
You're done! Happy customizing~