Add specific "Service" types for schema.org in WP Product Review

You might be reviewing some type of product that is not necessarily physical, like a delivery service, a list of radio shows or several financial services. In this case the available schemas don't help you so you need to enable the specific types for intangible services.

First, make sure you have the Classic Editor installed and actived so you have access to the schema.org options in the reviewed post/page.
Then, install and activate the My Custom Functions plugin which allows you to add the PHP snippet which is required to enable the schema.org intangible services.

Paste the following code in the PHP inserter box of the plugin:

add_action('admin_init', 'wppr_remove_old_schema');
function wppr_remove_old_schema(){
	delete_transient('wppr_schema_types_74e304ef41199bf81a830f3e5c6d2488');
}

add_filter('wppr_schema_things', 'wppr_schema_things', 10,1);
function wppr_schema_things($things){
	$things['Intangible'] = array( 'Service' );
	return $things;
}

Make sure you set the inserter to "ON" and save the changes.

After you've saved the changes make sure you comment out the add_action (first line) and saved again in order to not affect the performance of your website.