Add this link to your toolbar: Tag issue!

  var tags = jQuery('#edit-taxonomy-vocabulary-9-und').val();
  var add_comma = tags.length > 0;
  tags = jQuery.map(tags.split(', '), jQuery.trim);
  if (jQuery.inArray('Amsterdam2014', tags) === -1) {
    if (add_comma) {
       jQuery('#edit-taxonomy-vocabulary-9-und').val(jQuery('#edit-taxonomy-vocabulary-9-und').val() + ', Amsterdam2014');
    } else {
       jQuery('#edit-taxonomy-vocabulary-9-und').val( 'Amsterdam2014');
    }
  }

Please use the bookmarklet builder to encode the js code