subpages-list-cpt.php

<?php 

/**
 * Function to check if the current Page is a parent or not.
 * @return bool true (1) if the current Page has children else false (0)
 */
function wpdd_is_parent_page() {
    // Load details about this page.
    $post = get_post();

    $children = get_posts(array('child_of' => $post->ID, 'post_type' => 'service')) ;
	
    return is_single() && count( $children ) > 0;
    
}

//Add wpdd_is_parent_page as dynamic data to conditions = 1

?>