On the video, i explain moving the nodes using using the sub-gizmo.
But 2 things what you said are:
> (Bug) 1) When clicking on the terrain, it should be going to the mouse cursor. not the centre of the screen.
> 2) The node placed in the editor is because the raycast failed to hit something, possibly due to looking up to high when adding a node. This isn't a bug, In theory it shouldn't place a node if the raycast did not hit a surface(terrain or mesh), rather than sticking the node high in the sky in your case. The node is placed 10 units from the camera if it fails to find a hitspot, but i will make it not add a node instead.
Try on a default scene like the video to understand the workflow. I am going to go fix these 2 points you have brought up though.

Sorry for any inconvenience caused.