Fonctionality to alter wplink plugin. Adds new checkboxes to define rel attribute in <a> tag with noopener, noreferer, sponsored, nofollow and/or external values

post-wplink.js

/**
 * Fonctionality to alter wplink plugin,
 * Adds new checkboxes to define rel attribute in <a> tag with noopener, noreferer, sponsored, nofollow and/or external values.
 * Enqueue with admin_enqueue_scripts on post.php and post-new.php
 * wp_enqueue_script( 'post-wplink', "/url/to/post-wplink.js", ['wplink'], $version, true );
 * wlink-open event occurs when Insert/edit link modal box opens
 * wpLink.buildHtml function replaces the function from wplink.js
 * The string translate.mark_as_string might be define with localize_script(), contains __( 'Mark as <code>%s</code>', $textdomain );
 * Values that may be added to the rel attribute are defined in the rels array.
 * We push down the search terms div of shift=140 px and expand the modal height to 600 px. You may set these values to whatever you want. 
 * Xavier Birnie-Scott
 * 2020-12-07
 */
($ => {
   const rels = ['noopener', 'noreferer', 'sponsored', 'nofollow', 'external'];
   const mark_as = translate.mark_as_string;
   const shift = 140;
   const modal_height = 600;

   $(document).on('wplink-open', wrap => {
      // Sets the height of the modal
      $('#wp-link-wrap').height(modal_height);
      // Adds 4 checkboxes
      if (! $('[name="noopener"]').length) {
         // Appends checkboxes
         const $linkOptions = $('#link-options');
         rels.forEach(el => {
            const label = mark_as.replace(/%s/, el);
            $linkOptions.append('\
            <div><label><span></span>\
               <input type="checkbox" name="' + el + '"/> ' + label + '\
            </label></div>');
         });
         // Position of #most-recent-results div
         const $mostRecentResults = $('#most-recent-results');
         $mostRecentResults.css('top', parseInt($mostRecentResults.css('top')) + shift + 'px');
      }
   });

   // Overrides wpLink.getAttrs function from wplink.js
   window.wpLink.getAttrs = () => {
      wpLink.correctURL();

      var relation = '';
      rels.forEach(rel => {
         relation += $('[name="' + rel + '"]').prop('checked') ? `${rel} ` : '';
      });
      relation = relation.trim();

      return {
         href: $.trim($('#wp-link-url').val()),
         target: $('#wp-link-target').prop('checked') ? '_blank' : null,
         rel: relation.length ? relation : null
      };
   };

})(jQuery);

Since 4.7.4, wordpress adds noopener noreferrer on links that have a target attribute. When the post is saved, missing values are added to the rel attribute if the target attribute exists. This is done in wp-includes/formatting.php. To change this behavior, use the wp_targeted_link_rel filter to change the string 'noopener noreferrer'.