From https://once.com/writebook

app/views/leafables/_edit_header.html.erb

@@ -0,0 +1,18 @@
+<nav>
+  <%= link_to_previous_leafable(leaf, hotkey: false, for_edit: true) %>
+
+  <div class="breadcrumbs">
+    <%= render "books/index_link" %>
+    <span class="flex-item-no-shrink">▸</span>
+    <%= link_to book.title, book_slug_path(book) %>
+    <span class="flex-item-no-shrink">▸</span>
+    <%= form_with model: [ book, leaf ], url: leafable_path(leaf), class: "flex align-center gap-half", format: :html do |form| %>
+      <strong class="min-width"><%= form.text_field :title, form: "leafable-editor", class: "input full-width", autocomplete: "off" %></strong>
+    <% end %>
+  </div>
+
+  <button class="btn" data-action="fullscreen#toggle" data-fullscreen-target="button">
+    <%= image_tag "expand.svg", aria: { hidden: true }, size: 24 %>
+    <span class="for-screen-reader">Enter fullscreen</span>
+  </button>
+</nav>