Hi Motivatedclock! Thanks for your feedback, I'll keep it in mind for future updates. Adding a Gizmo that displays the SOI would be very useful.
The node isn't a physics node because it's necessary to keep orbital physics separate from collision physics; you need to manage it within your game. I recommend keeping the orbital system separate with just the OrbitalObject3D tree, where you can use real-world magnitudes, and separating the visible world with nodes that take positions, applying scales and deciding whether to use orbital position or follow other physics.
Thanks again for your feedback.