Thanks to BerndJM in the german forum I got a
solution: If you use show_menu2 and modify the menu call like this:
<?php
ob_start();
show_menu2(1, SM2_ROOT, SM2_ROOT, SM2_CURR|SM2_PRETTY);
$menu = ob_get_contents();
ob_end_clean();
$menu = str_replace('<br />', '<br />', $menu);
echo $menu;
?>
you can put as many <br /> in the menu title as you want. Only negative aspect: the filenames will look a little weird then.
Regards
Jochen