--- /dev/null
+/**
+ * Implements hook_form_system_theme_settings_alter().
+ */
+function {{ machine_name }}_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state) {
+ // Add a checkbox to toggle the breadcrumb trail.
+ $form['toggle_breadcrumb'] = [
+ '#type' => 'checkbox',
+ '#title' => t('Display the breadcrumb'),
+ '#default_value' => theme_get_setting('features.breadcrumb'),
+ '#description' => t('Show a trail of links from the homepage to the current page.'),
+ ];
+}