Hello Marius,
Most of Nevron UI controls have property Renderer that corresponds to respective type that cares how the control should be rendered.
The common pattern is to inherit this renderer and override the methods that render a part of the control and setup the Render property to a object of that inherit class.
The good news is that we had the same question before and we already have such inherited renderer implemented.
Please, find the attached cs file.
All you have to do is to create an instance of the new renderer and setup the Renderer property of NNavigationPane control:
MyNNavigationPaneRenderer renderer = new MyNNavigationPaneRenderer();
nNavigationPane1.Renderer = renderer;
Regards,
Angel.