Allows to display custom tabs on the Order Preview page in the Administration Area.
The event handler should accept two parameters - the controller object and the order object.
The handler should return an associative array of tab titles and corresponding tab partials.
public function subscribeEvents()
{
Backend::$events->addEvent('shop:onExtendOrderPreviewTabs', $this, 'extend_order_tabs');
}
public function extend_order_tabs($controller, $order)
{
return array(
'My tab caption' => 'modules/my_module/partials/_my_partial.htm',
'Second custom tab' => 'modules/my_module/partials/_another_partial.htm'
);
}