Resolve #3444843 "Integrate tour with navigation"

templates/block--navigation--tour.html.twig

+{#
+/**
+ * @file
+ * Default theme implementation to display the tour navigation item.
+ *
+ * Available variables:
+ * - content: The content of this navigation_tour_block.
+ *
+ * @ingroup themeable
+ */
+#}
+<div{{ attributes.addClass('toolbar-block') }}>
+  {% block content %}
+    {% set attr = content['#attributes'] %}
+    {% include '@navigation/toolbar-button.html.twig' with {
+      attributes: attributes.setAttribute('data-drupal-tooltip', content['#value'])
+      .setAttribute('type', content['#tag']).setAttribute('class', attr.class)
+      .setAttribute('aria-haspopup', attr['aria-haspopup'])
+      .setAttribute('disabled', attr.disabled),
+      icon: 'help',
+      html_tag: content['#tag'],
+      text: content['#value'],
+    } only %}
+  {% endblock %}
+</div>

tour.module

@@ -231,3 +231,35 @@ function tour_tour_tips_alter(array &$tour_tips, EntityInterface $entity): void
     }
   }
 }
+
+/**
+ * Implements hook_preprocess_HOOK() for navigation.html.twig.
+ */
+function tour_preprocess_navigation(&$variables) {
+  if (isset($variables['content']['content'])) {
+    $tour_block = \Drupal::service('plugin.manager.block')->createInstance('tour_button_block', []);
+    $tour = $tour_block->build();
+    $variables['content']['content']['tour'] = [
+      '#theme' => 'block__navigation__tour',
+      '#configuration' => $tour_block->getConfiguration(),
+      '#plugin_id' => $tour_block->getPluginId(),
+      '#base_plugin_id' => $tour_block->getBaseId(),
+      '#derivative_plugin_id' => $tour_block->getDerivativeId(),
+      '#in_preview' => FALSE,
+      '#weight' => 0,
+      'content' => $tour['content'],
+    ];
+  }
+}
+
+/**
+ * Implements hook_theme().
+ */
+function tour_theme($existing, $type, $theme, $path) {
+  $items['block__navigation__tour'] = [
+    'render element' => 'elements',
+    'base hook' => 'block',
+  ];
+
+  return $items;
+}