No, then you'd better redeclare the method getKeyTitlesPairs in the BxTemplSearch class of your template. It should have a look like:

private function getKeyTitlesPairs ()

    {

        $a = array();

        foreach ($this->aClasses as $sKey => $r)

if ($sKey == 'bx_timeline' || $sKey == 'bx_timeline_cmts')

continue;

            if ($this->_sMetaType || $r['GlobalSearch'])

                $a[$sKey] = _t($r['title']);

        return $a;

    }

The bold part is the addon to exclude Timeline and Timeline comments form the search keyword form.

Thanks LeonidS . getKeyTitlesPairs () changes the list of options/vlaues appearing under 'Section' of the search form only, but does not exclude timeline from search results when the 'global search' / 'select all' option is chosen. it sounds that we need to do something with the public function getForm() with BxBaseSearch class. any ideas?