When Resubscribing, add a simple product in WooCommerce Subscriptions

I am using WooCommerce Subscriptions plugin

I have a Subscription product that is linked to a WooCommerce simple product with custom pricing as a package to customer.

During Subscription renewal, I programmatically add the simple product to the active subscription.

I have a scenario, where customer cancels the subscriptions and Admin approves the cancellation of subscription.

In that case, in the customer My account subscription page, It displays a Re-subscription button. This re-subscription only takes the last cancelled subscriptions Subscription product and proceeds to checkout.

Is there any way I can add the simple products also during the re-subscription process?

I tried the below hook, but it works after new subscription creation:

add_action('wcs_create_subscription', 'action_wcs_create_subscription', 10, 20)

Is there a way to hook in to re-subscription process and add additional simple products to the checkout?

You can easily detect when a re-subscription in cart.

In the following code you will define the simple product ID to be added on re-subscription and the targeted subscription product ID in cart.

The code will add your simple product to cart when a customer re-subscribe via its My account Subscriptions (for a specific product subscription).

The code:

add_action( 'woocommerce_checkout_init', 'add_product_with_resubscription' );
function add_product_with_resubscription() {
    $cart = WC()->cart;

    $simple_product_id = 18; // Define the simple product ID to be added
    $subscr_product_id = 138; // Define the targeted product subscription ID
    $simple_is_in_cart = $is_resubscription = false; // Initializing

    // Loop through cart items
    foreach ( $cart->get_cart() as $item ) { 
        // Check for a specific resubscription
        if( isset($item['subscription_resubscribe']) 
        && in_array($subscr_product_id, [$item['product_id'], $item['variation_id']]) ) {
            $is_resubscription = true;
        }
        // Check that the simple product is not yet in cart
        if( $simple_product_id == $item['product_id'] ) {
            $simple_is_in_cart = true;
        }
    }

    // Add to cart the simple product and recalculate totals
    if ( $is_resubscription && !$simple_is_in_cart ) {
        $cart->add_to_cart($simple_product_id);
        $cart->calculate_totals();
    }
}

Code goes in functions.php file of your child theme (or in a plugin). Tested and works.