In case that you want something like this:
Advantage is, you can change between users with only one click, just go to user you want to log in and click on it, just like changing navbar tabs (I use its class in this modification).
It works with all vB4 versions (even vB4.2), but you need to make one manual template edit:
Edit
navbar template and find there:
HTML Code:
<div class="body_wrapper">
Add below:
HTML Code:
{vb:raw template_hook.navbar_after_links2}
It adds new hook, that's why it works with all vB4 versions. After that import attached version. You could place it on other places too, but I like it above breadcrumb, as shown on picture above.