I'm trying to create a drop down menu in active admin's navigation. The docs: 

<https://activeadmin.info/2-resource-customization.html#customize-the-menu>

says all I need to do is create the menu: 

```
    config.namespace :admin do |admin|
      admin.build_menu do |menu|
        menu.add label: 'example', priority: 0
      end
    end

```

then add that menu as the parent of the resource: 

```
menu parent: 'example'

```

But that doesn't work for me.

The only thing that has thus far is this:

```
    config.namespace :admin do |admin|
      admin.build_menu do |menu|
        menu.add label: 'Appointment', priority: 0, html_options: { target: :blank } do |item|
          item.add label: 'Appointment',  url: '/admin/appointments'
          item.add label: 'AppointmentCommunication',  url: '/admin/appointment_communications'
        end
      end
    end

```

With menu: false in the actual resource file.

But that's pretty messy, and not well organized. I was hoping to have a simpler way of making the menus. But maybe I'm just missing something. 

Note: I did try to name the menu something that wasn't the name of one of the resources but alas no changes. Additionally, I tried moving the two resources - Appointment and AppointmentCommunication - into a folder called Appointment but obviously that didn't work. 

Any thoughts on this would be appreciated.