[kh99]

The "Show Permission Name" field (if you use it) needs to be a dot-separated list of keys into the $show array (which is a global variable used in the vb code), and the tab will only be shown if they are all true. In your case, I'm assuming there is no $show variable that matches the if statement in your existing code. So you could make a plugin to set a variable in the $show array. But I think maybe the easiest thing would be for you to leave the "SHow Permission Name" field blank, and create a plugin using hook check_navigation_permission and set the variable $retval to true or false depending on if you want your tab to show, something like:

if ($retval && $data['name'] == 'identity')
{
    $retval = in_array($vbulletin->userinfo['userid'], array(20,2000,3611,14507));
}

where you'd replace identity (in red above) with the "Identity" value for your tab (as shown in the navigation manager).

To answer your other question, the THIS_SCRIPT field is to decide when your tab should be highlighted as the current tab. Since yours seems to go to the admincp where the tabs aren't shown, you don't need to worry about highlighting (so leave it blank). Same with "Append 'tabid' to URL" - that also has to do with highlighting the current tab.