Hi Artenio,
The Vector Image Manager window is under Window/MaterialUI/VectorImageManager :)
The next version, v1.1.0, will contain a lot of performance improvements (especially for MaterialButton, ScreenView, and the tweening system) and some quality-of-life improvements, as well as a couple of new features. We're hoping to submit that to the store for approval early next week.
For the most part, you should be able to upgrade without much extra work (The difference is *far* less than between the GitHub version and this one ).
Cheers, and let us know if you have any other questions :)
~Declan.