>>718576632
using view ports is the hack and it's stupid and inefficient.
The little rectangle in the top right is displaying a "render target" a custom canvas that can be stored in the GPU. It doesn't need to be part of your scene or shown on any camera, it can just be stored internally, separate to your main render target which is your game window.
It's dynamic and can be used as a texture and in shaders.
even the N64 had this feature, but Godot does not.