Sub-menus in RISE courses

Hi,

I'm looking for a way to have sub-menus in the menu list. Currently, I see that we can use section and lessons. So basically, it's just a 2-level structure, while I need 3-level. I remember seeing other discussions on this, but no solution to it as yet. 

Maybe I missed something?

This is what I need:

Module 1: Introduction

Topic 1: Overview

Sub-topic 1:

Sub-topic 2:

...

Sub-topic n:

Topic 2: Architecture

Sub-topic 1:

Sub-topic 2:

...

Sub-topic n:

Module n: Best Practices