You can use the UserMenuService offered by the Web SDK to add another item in this list.
There is also a hookDocs and the docs application option that allows you to add documentation links. These links would then show up in the documentation section:
In addition to the above methods: in 1018.0.0 we’ve introduced a hookDrawer that allows to place your own components in the navigation or the right drawer.
As always, samples for these extension points can be found in the tutorial application.