Add, remove course levels from Tutor LMS Plugin

tutor-lms-add-remove-course-level.php

add_filter('tutor_course_level', 'add_custom_course_level_tutor');

/**
 * @param $levels
 * @return mixed
 * 
 * Add, remove course levels
 */
if ( ! function_exists('add_custom_course_level_tutor')) {
    function add_custom_course_level_tutor($levels){
        /**
         * Add Levels
         */

        $levels['custom_level_1'] = __('Custom Level 1', 'text-domain');
        $levels['custom_level_2'] = __('Custom Level 2', 'text-domain');
        $levels['custom_level_3'] = __('Custom Level 3', 'text-domain');

        /**
         * Remove Level
         */
        if (isset($levels['existing_level_key'])) {
            unset($levels['existing_level_key']);
        }

        if (isset($levels['existing_level_key_2'])) {
            unset($levels['existing_level_key_2']);
        }

        return $levels;
    }
}