how to project a 2d node on top of my canvas layer

Add another canvas layer and the 2d node in it?

edit: it's also important to understand the scenetree and the node order: https://docs.godotengine.org/en/stable/getting_started/step_by_step/scene_tree.html#tree-order https://github.com/godotengine/godot/issues/8163

In the scene tree, whilst this isn't entirely the correct way to think about it but if you so wish you can start out by thinking of nodes towards the top of the scenetree as being the bottom layers in say photoshop. So they get drawn under the ones that are further below in the scenetree.

The better and more correct way to think about it though is that things get drawn in scenetree order, so obviously the first thing in the list gets drawn underneath the second since it is drawn first and then the second thing gets drawn on top of it.