There are many different ways that you can setup the menus – and yes you can have a submenu under a submenu. Here’s the guide on using our menus.
If you have any further questions, please let us know.
Thanks for your question about the submenus. At the time of the question above, the issue could not be resolved without custom coding – to my knowledge. I tested this on my own test site and I need to point out a few things first. The menu items that you see with a default installation include Post Type Archive, Series, and Podcast.
The default list of items (pages, posts,etc) do not include the post types described and shown in the original question. These can be added using a plugin or custom coding in WordPress. I believe that this is the reason that the menu was not displaying the sub-menus or sub-sub-menus. I loaded a plugin called Custom Post Type UI and then added one of the custom post types – Post Type Archive. I also noticed that the question included a label that did not need to be a post type (Series). I tested the structure by creating a Category called “January”. I then created a submenu and a submenu item as you can see above. Once it’s created, you have to publish the changes to save them. When I reviewed the menu I could see that it was working.
So, at least for me, the sub-sub-menus are working. However, I’ll take it one step further and create two other custom menu items- Months and Past Year. Even with the three custom post types I was able to see that the menus were working.
Please double-check your versions of the plugins and WordPress version. As far I can see they are working. If you have further questions please let us know.