As of 5.2.3 it is no longer present AT ALL in new installs.
Here's how to make it work on any page if it does already exist. (If it doesn't exist, instructions for adding it back are at the bottom, but you still need to do this part!)
First, go to AdminCP > Style Manager, and from your chosen style, select "Add New Template" from the dropdown.
Template title: mark_read
Template contents:
Code:
<script>
(function($) {
//apply to Search Results widget only
//if ($('.search-results-widget').length) {
//attach click handler to Mark Channels Read subnav item
$('.navbar_mark_channels_read').on('click', function(e) {
e.preventDefault();
e.stopImmediatePropagation(); //cancel original click handler
//mark channel read for root node 1 to mark all channels read
vBulletin.setChannelRead(1, {
success: function() {
location.href = pageData.baseurl; //redirect to homepage
},
error: function() {
openAlertDialog({
title: vBulletin.phrase.get("forum"),
message: "Mark Channels Read failed.",
iconType: "error"
});
}
});
});
// }
})(jQuery);
</script>
Hook Location: footer_before_body_end
Title: Mark Channels Read Fix
Template Name: mark_read
Leave all other fields as they are, and save.
If it DOES NOT exist:
Create a new navbar item in site-builder called "Mark channels read" or whatever. Then in the link creation dialog under Target URL, put http://yourforumurl.com/# and under link attributes, put class="navbar_mark_channels_read" and save.
Obviously replace yourforumurl.com with your actual forum url.
Original fix posted by Glenn Vergara on www.vbulletin.com/forum