The dark sidebar in the site editor utilises a drill down pattern to expose subsequent levels of navigation.

At the root level of Design, we indicate this behaviour by appending a chevron to each menu item:

However, in each of the other panels, this chevron does not appear, despite the menu items having the same behaviour:

We should be consistent so that users are better able to predict how the UI will behave. That means either removing the chevrons at the root, or adding them to the other panels.

Important note: We already use the small chevron icon in the Navigation panel to indicate the presence of a submenu:

This is an established pattern in List View as well. If we elect to use chevrons as a universal drilldown indicator for menu items in the dark sidebar, then we need to make sure there's no confusion between the two.