^^&&^^

Edit File: class-walker-docs.php

<?php
/**
 * Custom page walker for docs.
 *
 * @package documentor
 */

/**
 * Documentor Docs Walker
 */
class Documentor_Walker_Docs extends Walker_Page {
	/**
	 * Parent doc.
	 *
	 * @var mixed
	 */
	public static $parent_item = false;

/**
	 * Parent doc class.
	 *
	 * @var string
	 */
	public static $parent_item_class = '';

/**
	 * Start level.
	 *
	 * @param string  $output - output.
	 * @param integer $depth - depth.
	 * @param array   $args - arguments.
	 */
	public function start_lvl( &$output, $depth = 0, $args = array() ) {
		$indent  = str_repeat( "\t", $depth );
		$output .= "\n$indent<ul class='children'>\n";

if ( $args['has_children'] && 0 === $depth ) {
			$classes = array( 'page_item', 'page-item-' . self::$parent_item->ID );

if ( self::$parent_item_class ) {
				$classes[] = self::$parent_item_class;
			}
		}
	}

/**
	 * Start element.
	 *
	 * @param string  $output - output.
	 * @param int	 $page - page id.
	 * @param integer $depth - depth.
	 * @param array   $args - arguments.
	 * @param integer $current_page - current page id.
	 */
	public function start_el( &$output, $page, $depth = 0, $args = array(), $current_page = 0 ) {

if ( 0 === $depth ) {
			self::$parent_item = $page;
		}

if ( $page->ID === $current_page ) {
			self::$parent_item_class = 'current_page_item';
		} else {
			self::$parent_item_class = '';
		}

// add the number of childrens.
		$show_number_childrens = isset( $args['pages_with_children'][ $page->ID ] ) && documentor()->get_option( 'sidebar_show_nav_number_of_childs', 'documentor_single', true );
		if ( $show_number_childrens ) {
			$childs			 = get_pages(
				array(
					'child_of'  => $page->ID,
					'post_type' => $page->post_type,
				)
			);
			$count			  = count( $childs );
			$args['link_after'] = ( isset( $args['link_after'] ) ? $args['link_after'] : '' ) . ' <sup>[' . $count . ']</sup>';
		}
		$args['link_before'] = ( isset( $args['link_before'] ) ? $args['link_before'] : '' ) . ( !empty( $args['icon'] ) ? ' <i class="'.$args['icon'].'"></i>' : '' );

parent::start_el( $output, $page, $depth, $args, $current_page );
	}
}