diff --git a/book/src/todo_4.md b/book/src/todo_4.md
index 55d97e7c6fc8..99d8f2d5f881 100644
--- a/book/src/todo_4.md
+++ b/book/src/todo_4.md
@@ -11,9 +11,9 @@ We will start by adding an empty sidebar without any functionality.
There are a couple of steps we have to go through to get to this state.
First, we have to replace [`gtk::ApplicationWindow`](https://gtk-rs.org/gtk4-rs/stable/latest/docs/gtk4/struct.ApplicationWindow.html) with [`adw::ApplicationWindow`](https://world.pages.gitlab.gnome.org/Rust/libadwaita-rs/stable/latest/docs/libadwaita/struct.ApplicationWindow.html).
-The only difference between those two is that `adw::ApplicationWindow` has no titlebar area.
-That comes in handy when we build up our interface with [`adw::Leaflet`](https://world.pages.gitlab.gnome.org/Rust/libadwaita-rs/stable/latest/docs/libadwaita/struct.Leaflet.html).
-In the screenshot above, the `Leaflet` behaves like a [`gtk::Box`](https://gtk-rs.org/gtk4-rs/stable/latest/docs/gtk4/struct.Box.html) and contains the collection view on the left, a separator in the middle and the task view on the right.
+The main difference between those two is that `adw::ApplicationWindow` has no titlebar area.
+That comes in handy when we build up our interface with [`adw::NavigationSplitView`](https://world.pages.gitlab.gnome.org/Rust/libadwaita-rs/stable/latest/docs/libadwaita/struct.NavigationSplitView.html).
+In the screenshot above, the `NavigationSplitView` adds a sidebar for the collection view to the left, while the task view occupies the space on the right.
When using `adw::ApplicationWindow` the collection view and task view have their own [`adw::HeaderBar`](https://world.pages.gitlab.gnome.org/Rust/libadwaita-rs/stable/latest/docs/libadwaita/struct.HeaderBar.html) and the separator spans over the whole window.
@@ -56,12 +56,10 @@ Filename:
@@ -73,85 +71,99 @@ The adaptive behavior of the leaflet allows the To-Do app to work on smaller scr
We add the necessary UI elements for the collection view, such as a header bar with a button to add a new collection, as well as the list box `collections_list` to display the collections later on.
-
-As you can see in the screencast above, the header bar also displays a close button if the leaflet is folded.
-We include this logic with an expression which can be built up in the UI file with the tag [`lookup`](https://gtk-rs.org/gtk4-rs/stable/latest/docs/gtk4/struct.Expression.html#gtkexpression-in-ui-files).
+We also add the style [navigations-sidebar](https://gnome.pages.gitlab.gnome.org/libadwaita/doc/1-latest/style-classes.html#sidebars) to `collections_list`.
Filename: listings/todo/7/resources/window.ui
```xml
-