Library on top of OpenTK?

Hello everyone,

I would like to develop a basic 3D editor and OpenTK seems to be the best solution for me. A full game engine would bring me too many useless features and make me lose some portability I would have with OpenTK. But I feel like reinventing the wheel coding a method to draw a cube, a sphere etc. As well as getting events for a on hit or these kind of classic features. But I am surprised to not find any library implementing these.
Am I just really bad with google or is there really nothing like this around there?

Thanks to have read me

PS: sorry for my limited English.