course_details_widget_custom_fields.php

add_filter('wplms_course_details_array','wplms_custom_course_details_information');
function wplms_custom_course_details_information($course_details){
  $course_details['custom']= array(
    'label' => 'custom',
    'callback' =>  false,
  );      
  return $course_details;
}

add_filter('wplms_course_details_widget','custom_info_course_widget',999999);
function custom_info_course_widget($course_details){
  $course_details['custom'] = "<li>I am a custom Detail<i class='fa fa-dribbble'></i></li>";
 return $course_details;
}