I created an ARKit app using SceneKit Framework. I want to bring it over to ARCore but using straight OpenGL seems daunting.
Is there a high-level scene graph framework like SceneKit for Android developers that can help to import and render 3D models?
ViroCore is a SceneKit for Android. With ViroCore you describe scenes at a high level in Java, without having to implement rendering algorithms yourself in OpenGL. It has built-in integration with ARCore, and its rendering feature-set is equivalent to SceneKit.
It's also thoroughly documented, with development guides, a full Javadoc, and code samples. A good starting point is trying out this AR retail code sample -- it's a full ARCore application written with ViroCore.