Add Previous / next lesson links to the Lifter LMS.

functions.php

<?php


/**
 * Add Default Previuos / Next lesson pagination to the lesson template of Lifter LMS
 */
add_action( 'wp', 'add_lifter_lesson_navigation' );
function add_lifter_lesson_navigation(){
	if ( class_exists( 'LifterLMS' ) ) {
		if ( is_lesson() ) {
			add_action( 'lifterlms_single_lesson_after_summary', 'lifterlms_template_lesson_navigation', 20 );
		}
	}
};