Are there any extension for the Touch Bar?

I just discovered in the Extensions menu in System Preferences that there is a sub menu for the Touch Bar, and after a quick inline research I was wondering if there actually are any extensions for the Touch Bar.

I know that there is a program called "BetterTouchTool" that allows you to customise different settings on your Mac, but it doesn't work for me. Probably because I run beta software on my machine.

So, are there extensions for the Touch Bar and if so how do you get your hands on them? And if there aren't any extensions, what is the deal with the sub menu?