Allow logged users to submit review for course

Yes, this is already in the features. If StudentA is a part of courseA, only he is allowed to submit a review. A non logged in user, or a user who is not a part of courseA, will never get the option to post a review on that course

Okay, then just add a check in the code below for logged in users only Add this code in your wplms customizer plugin > wplms-customizer.php

add_action('wplms_after_course_description','myreview_button');
function myreview_button(){
    $course_id = get_the_ID();
    $user_id = get_current_user_id();
    ?>
    <form action="<?php echo get_permalink($course_id); ?>" method="post">
    <input type="submit" name="review_course" class="review_course unit_button full button" value="<?php _e('REVIEW COURSE ','vibe'); ?>" />
    <?php wp_nonce_field($course_id,'review'); ?>
    </form>
    <?php
 
}

After course description it will show a button like this: http://prntscr.com/vieuuo And on clicking that, it will show that review form It doesn't matter whether the current logged in user purchased the course or not, or it's just a free course. This review button will be visible there