Issue #2958532: Integration with LinkIt using an Anchor Link Matcher plugin...

    $libraryUrl = $this->getLibraryUrl();

    return [

      'Link' => [

        'label' => $this->t('Link'),

      'LinkToAnchor' => [

        'label' => $this->t('Link to anchor'),

        'image' => $libraryUrl . '/icons/link.png',

      ],

      'Unlink' => [

        'label' => $this->t('Unlink'),

        'label' => $this->t('Unlink anchor'),

        'image' => $libraryUrl . '/icons/unlink.png',

      ],

      'Anchor' => [

<?php

namespace Drupal\anchor_link\Plugin\Linkit\Matcher;

use Drupal\Component\Utility\Html;

use Drupal\linkit\MatcherBase;

use Drupal\linkit\Suggestion\DescriptionSuggestion;

use Drupal\linkit\Suggestion\SuggestionCollection;

/**

 * Provides specific linkit matchers for Anchor links.

 *

 * @Matcher(

 *   id = "ckeditor_anchor_link",

 *   label = @Translation("CKEditor Anchor link"),

 * )

 */

class CKEditorAnchorLinkMatcher extends MatcherBase {

  /**

   * {@inheritdoc}

   */

  public function execute($string) {

    $suggestions = new SuggestionCollection();

    $string = ltrim($string, '#');

    $suggestion = new DescriptionSuggestion();

    $suggestion->setLabel($this->t('#@anchor_link', ['@anchor_link' => $string]))

      ->setPath('#' . $string)

      ->setGroup($this->t('Anchor links (within the same page)'));

    $suggestions->addSuggestion($suggestion);

    return $suggestions;

  }

}