[fromtheflames]

overkill yes, but the first (and perhaps the only) that I was able to think; any new suggestion is welcome

step by step? uh let's try
1) go to "plugins and products" in your admincp
2) at the bottom, click "add new plugin"
3) select "vbulletin" as product, "editor_toolbar_set" as hook, pick a descriptive name as title, leave execution order as is, and add the following as php code

PHP Code:

$newButton = array('Templates'); 
$this->config['toolbar'][] = $newButton; 


I used 'Templades' in the newButton array because I want that button, but you might replace it with the button you need.