Is there any way to "see" in the editor nodes inside an instanced scene from the containing scene?

I have a scene instanced in another and would like to access certain nodes within it from the containing script.

This would be something akin to exporting a var

Specifically the instanced scene contains rigid bodies I would like to bind to a joint that exists in the containing scene.

You can use get_node() access child nodes of the instanced scene, even if they're not visible in the editor per se.

Also, you can view and edit children in the editor by right-clicking the instanced scene in the Scene tree dock then toggling Editable Children.

Ah exactly what I am looking for thanks.