Read your error log again:

add_submenu_item change on this function elgg_register_menu_item

Just change your code with

elgg_register_menu_item(elgg_echo('videochat:menu:rooms'), $CONFIG->wwwroot."pg/videochat");

And please, don't make duplicate posts

When I change this function I don't look in menu link.

This code not for 'Menu' link

For adding link to 'Menu' you need register items for 'site' array

$item = new ElggMenuItem('videochat', elgg_echo('videochat:index:title'), 'videochat');
elgg_register_menu_item('site', $item);

 

Try now again

.

error

Error after change function

Create file sidebar.php in mod\videochat\views\default\videochat\

With this code:

<?php
/**
 * Videochat sidebar
 */
 
if(elgg_get_plugin_setting("tokbox_method", "videochat") != "embed")
{
$create = elgg_get_site_url() . "videochat/create";
$videochatcreate = elgg_echo('videochat:menu:create');
$videos = elgg_get_site_url() . "videochat/";
$videochatrooms = elgg_echo('videochat:menu:rooms');
 
echo '<ul class="elgg-menu elgg-menu-page elgg-menu-page-default">
<li class="elgg-menu-item-bookmarklet">
<a title="';
echo $videochatrooms; echo '" href="';
echo $videos; echo'">';echo elgg_echo('videochat:menu:rooms');echo '</a><a title="';
echo $videochatcreate; echo '" href="';
echo $create; echo'">';echo elgg_echo('videochat:menu:create');echo '</a></li></ul>';
}
else {
$videochat = elgg_get_site_url() . "videochat/";
$videochattitle = elgg_echo('videochat:index:title');

echo '<ul class="elgg-menu elgg-menu-page elgg-menu-page-default">
<li class="elgg-menu-item-bookmarklet">
<a title="';
echo $videochattitle; echo '" href="';
echo $videochat; echo'">';echo elgg_echo('videochat:index:title');echo '</a></li></ul>';
}

echo elgg_view('page/elements/comments_block', array(
    'subtypes' => '',
    'owner_guid' => elgg_get_page_owner_guid(),
));

echo elgg_view('page/elements/tagcloud_block', array(
    //'subtypes' => '',
    'owner_guid' => elgg_get_page_owner_guid(),
));

Then add

$sidebar = elgg_view("videochat/sidebar");

in the mod\videochat\pages\create.php

and

$body = elgg_view_layout('two_column_left_sidebar', array(
    'content' => $content,
    'title' => $title,
    'sidebar' => $sidebar,
    ));

I create this file , but I don't look items on right side.