You may wanna consider creating a pluging since it's not avised to change the core code, especially this function could be override easily.
Find function qa_category_navigation_sub(){} in qa-aap-format.php and change it with this:
function qa_category_navigation_sub($parentcategories, $parentid, $selecteds, $pathprefix, $showqcount, $pathparams)
/*
Recursion function used by qa_category_navigation(...) to build hierarchical category menu.
*/
{
if (qa_to_override(__FUNCTION__)) { $args=func_get_args(); return qa_call_override(__FUNCTION__, $args); }
$navigation=array();
if (!isset($parentid))
$navigation['all']=array(
'url' => qa_path_html($pathprefix, $pathparams),
'label' => qa_lang_html('main/all_categories'),
'selected' => !count($selecteds),
'categoryid' => null,
);
if (isset($parentcategories[$parentid]))
foreach ($parentcategories[$parentid] as $category)
$navigation[qa_html($category['tags'])]=array(
'url' => qa_path_html($pathprefix.$category['tags'], $pathparams),
'label' => $category['qcount']>0 ? qa_html($category['title']) :null,
'popup' => qa_html(@$category['content']),
'selected' => isset($selecteds[$category['categoryid']]),
'note' => $category['qcount'] > 0 ? ('('.qa_html(number_format($category['qcount'])).')') : null,
'subnav' => qa_category_navigation_sub($parentcategories, $category['categoryid'], $selecteds, $pathprefix.$category['tags'].'/', $showqcount, $pathparams),
'categoryid' => $category['categoryid'],
);
return $navigation;
}
That should help you out