Ok this is possible, there are two ways to tackle this

1. Hide the Curriculum button for non-logged in members
2. Show an error message for users trying to check out curriculum

3. 1+2

The safest and recommended way is 3. So here is how you can achieve this :

1. Go to WP Admin -> Plugins -> Editor -> WPLMS Customizer -> customizer_class.php

2. Add the following code in __construct function :

PHP Code:

 

add_filter('wplms_course_nav_menu',array($this,'custom_course_nav_menu'));
add_action('bp_before_course_body',array($this,'reset_action_curriculum'));

 

3. Add the following function in class :

PHP Code:

 

function custom_course_nav_menu($menu){
   if(!is_user_logged_in())
      unset($menu['curriculum']);

return $menu;
}

function reset_action_curriculum(){
  if(isset($_GET['action'])){
if( !is_user_logged_in() && $_GET['action'] == 'curriculum')
 wp_die('Curriculum can not be accessed without logging in.');
}

}