created my own wp-function „wp_list_bookmarks_v2“
located in „wp/wp-includes/bookmark-template“
( better to be included from outside of wp-folders, because of wp-updates.. )

i dont want to show links that have category=4 OR category=5 !!!

if i ask for links with category=4,5 then i mean
i want all links that have category=4 AND category=5 !!!

now, the script works fine for me
its a prototype, not giving you all the options of wp_list_bookmarks
its giving a list of links, target _blank, thats all

function wp_list_bookmarks_v2($args = '') {


    //////////////////////////////
    // ORIG:wp_list_bookmarks

	$defaults = array(
		'orderby' => 'name', 'order' => 'ASC',
		'limit' => -1, 'category' => '', 'exclude_category' => '',
		'category_name' => '', 'hide_invisible' => 1,
		'show_updated' => 0, 'echo' => 1,
		'categorize' => 1, 'title_li' => __('Bookmarks'),
		'title_before' => '
', 'title_after' => '
',
		'category_orderby' => 'name', 'category_order' => 'ASC',
		'class' => 'linkcat', 'category_before' => '
',
		'category_after' => '
'
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	$output = '';

    // ORIG:wp_list_bookmarks
    //////////////////////////////




    //////////////////////////////
    // CUSTOM:


    $debug = 0;

	// category_name category zerlegen in liste... split by ","
	// dann
	// wp_list_bookmarks($args = '')

    if ($debug==1) echo "
debug TRUE
"; // bedingung muss in klammern stehen!!!, beim einzeiler restliche anweisung muss nicht in {} stehen

    /*
	echo "args: ".$args ."
";

	echo "r:    ".$r ."
";

    echo "r['category']:    ".$r[category] ."
";

    $category_split = split(',', $r[category]);

    echo "category_split: " ."
" ;
    print_r( $category_split )."
";


    foreach ( $category_split as $single_cat ) {

       echo "single_cat: ".$single_cat."
";

    }
    */



    $my_bookmarks = array(); // counter key is link_id value is increased if it has the category
    $my_bookmarks_output = array(); // output complete links as arrays

    $category_split = split(',', $r[category]);

    if ($debug==1) echo " count( category_split ) ". count( $category_split ) ."
";

    $count_category_split = count( $category_split ); // anzahl der angefragten categorien

    if ($debug==1) echo "

";


    //////////////////////////////
    // ORIG:wp_list_bookmarks

	if ( $categorize ) {
		//Split the bookmarks into ul's for each category
		$cats = get_terms('link_category', array('name__like' => $category_name, 'include' => $category, 'exclude' => $exclude_category, 'orderby' => $category_orderby, 'order' => $category_order, 'hierarchical' => 0));


        //////////////////////////////
        // ORIG:wp_list_bookmarks

		foreach ( (array) $cats as $cat ) {
			$params = array_merge($r, array('category'=>$cat->term_id));

            if ($debug==1)  echo "cat->term_id: ".$cat->term_id . "
";
			//if ($debug==1)  echo "params: ";
			//if ($debug==1)  print_r( $params )."
";

			$bookmarks = get_bookmarks($params);
			if ( empty($bookmarks) )
				continue;

			if ($debug==1)  echo "bookmarks: ";

            // ORIG:wp_list_bookmarks
            //////////////////////////////



            /////////////////////////////
            // CUSTOM

			foreach ( (array) $bookmarks as $bookmark ) {


               if ($debug==1)  echo "
 bookmark link_id: 
";
			   if ($debug==1)  print_r($bookmark->link_id);
			   if ($debug==1)  echo "
";


			   if (array_key_exists( $bookmark->link_id , $my_bookmarks ) ){

			      if ($debug==1)  echo "array_key_exists: TRUE" ."
";

			      $my_bookmarks[ $bookmark->link_id  ] = $my_bookmarks[ $bookmark->link_id  ] +1;
			      }else{
			      if ($debug==1)  echo "array_key_exists: FALSE" ."
";

			      $my_bookmarks[ $bookmark->link_id  ] = 1; // counter
			      }

			      if ($debug==1)  echo "count:" .$my_bookmarks[ $bookmark->link_id  ] ."
";
                  if ($debug==1)  echo "count_category_split: ".$count_category_split."
";

                  if ( $my_bookmarks[ $bookmark->link_id  ] == $count_category_split ){

                     if ($debug==1) echo "OKKKKKKKKKKKKKKKKKKKKK
";

                     array_push($my_bookmarks_output, $bookmark);

                  }
            // CUSTOM
            //////////////////////////////

            }






			}

			if ($debug==1) echo "----------------------------------------------
";


//print_r( $my_bookmarks_output );

echo "
";
foreach ( $my_bookmarks_output as $bm ) {
 //echo "bm: ".$bm->link_id."
";
 $bookmark = get_bookmark($bm->link_id);
 echo ''.$bookmark->link_name.'
';
}



}







}