Define custom filter by default.

$viewdefs['Leads']['base']['filter']['basic']['filters'][] = array(
    'id' => 'filterLeadConverted',
    'name' => 'Não convertidos',
    'filter_definition' => array(
        array(
            'converted' => array(
                '$equals' => array(
                    false,
                ),
            ),
        ),
    ),
    'editable' => false,
    'is_template' => false,
);