Custom set of default quick tags in Wordpress

gistfile1.txt

function frl_quicktags_settings($qt_init, $editor_id){
    
    if($editor_id != 'content')
        return $qt_init; //not a default case
 
    /* default set of values - "strong,em,link,block,del,ins,img,ul,ol,li,code,more,spell,close,fullscreen" */;
    $qt_init['buttons'] = "strong,em,link,block,img,ul,ol,li,code,fullscreen"; ;
     
    return $qt_init;
}
add_filter('quicktags_settings', 'frl_quicktags_settings', 2, 2);