The Onemore add-in (download) provides you with a plethora of additional functions and snippets. One of them is a Table of Contents (ToC) function. You can access it in Onemore->Snippets:


After choosing, it will show you a window like below:


It allows us to make a ToC from three types of items; we will make the first option today. But before that, we need to make the sections into headings. Note that you can style them after choosing, just like in Word. Refer to the video below.
Step 1 : Making the desired sections into headings
If that’s done, we go back to step 1 : clicking on the ToC button. Refer to the video below:
Step 2 : Making the TOC
Voila! A Table of Contents with Onemore!
Hope this helps!