Where is template_hook.navbar_end defined and what does it do?

[stevefink]

I am using vBulletin 4.2.3. In my navbar template, the following code is available:

{vb:raw template_hook.navbar_end}

My question is, where do I find what exactly this is rendering? Is there somewhere that navbar_end is defined? The reason I ask is I upgraded vBulletin from 4.1.9 to 4.2.3 and a plugin that renders a link into my navbar isn't show up in my dev (upgraded) copy. the templates are exactly the same. I'm assuming navbar_end has some kind of definition and that's where it is being rendered (or not rendered in my case)
The specific plugin I'm referring to here is vmoods. I can't find any specific reason why it would work on production vs my dev upgraded copy. Templates are verbatim to each other (navbar, specifically). I'm trying to figure out what caused it to disable.

I'd imagine there's something going on in `template_hook.navbar_end` that's causing it to render on prod and not on dev.