How to remove Quicktabs cookie on certain page?
Finally solved it. In case anyone is stuck with the same problem, this code now works for me. I learned that it's important to always set the path, to be able to retrieve the same cookie on different pages. I never got $.removeCookie() to work, so instead I used a default value. Also it did not work to use true, false and undefined as values, but it worked to use them as text inside quotes, 'true', 'false' and 'undefined'. Slowly getting there :-).

      Drupal.behaviors.quicktabsHistory = {
        attach: function(context, settings) {       

        var default_tab = 'quicktabs-tab-instrument_flikar-0';
        if($.cookie('id', {path:'/'}) == 'undefined'){
            var id = $(this).attr('id');
        }else{
            var id = $.cookie('id', {path:'/'});
        }
        var tab = id;
        var flagga = $.cookie('flagga', {path:'/'});

        if($("body").is(".page-taxonomy")) {
            $.cookie('flagga', true, {path:'/'});
            $.cookie('id', default_tab, {path:'/'});
        }           

        $('.quicktabs-wrapper', context).each(function() {
            if (tab != '' &amp;&amp; flagga === 'false') {
              $(this).find('ul.quicktabs-tabs a#' + tab).click();
            }
            else {
              $.cookie('flagga', false, {path:'/'});                    
              $(this).find('ul.quicktabs-tabs a#' + default_tab).click();
            }

            $(this).find('ul.quicktabs-tabs a').click(function() {
                $.cookie('id', $(this).attr('id'), {path:'/'});
            });
        });
    };