WooCommerce add custom product_type_option

Your code only creates the checkbox, you need also to save the value like that

add_filter("product_type_options", function ($product_type_options) {

    $product_type_options["wildcard"] = [
        "id"            => "_wildcard",
        "wrapper_class" => "show_if_simple",
        "label"         => "Wildcard",
        "description"   => "Description",
        "default"       => "no",
    ];

    return $product_type_options;

});


add_action("save_post_product", function ($post_ID, $product, $update) {

    update_post_meta(
          $product->ID
        , "_wildcard"
        , isset($_POST["_wildcard"]) ? "yes" : "no"
    );

}, 10, 3);

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