... You could practice with the inspector then code yourself as far as individual code lines go.
The more I think about this the more I feel like your missing a fundamental design decision in how Godot works Namely these bits, but instancing in particular:
Basically, whatever you practice in the inspector/editor can, once you are happy with it, be saved as a .tscn and instanced into any other scene as a child.
You don't need to convert everything you did in the editor into code to be able to instance it at runtime, this would be insanely time-consuming and as you've noticed laborious. But the reason what you're trying to do is laborious is because nobody expected it to be done this way.
Instead, if you want to spawn one or more of something during runtime:
Rapidly prototype it in the editor using the inspector.
Save the node tree as a new scene (if you come from Unity, you can consider this now a prefab)
* Instance it as many times as you need in your main game scene.
Unless you can somehow type hundreds of lines faster than a handful of mouse clicks, this WILL be faster than to instance what you need entirely from code, and is the reason a GUI editor exists at all, to remove the need to code everything and speed up development (this isn't PyGame), but allow you to whenever you need to.
Now in your game scene you may want to update a specific attribute at runtime, that's fine and for that see my previous post about how to identify any attribute name in the inspector and use it in code.
But doing it this way ensures your code only needs to include the things that are actually likely to change at runtime, or are produced procedurally (geometry for example), and keeps typing superfluous code to a minimum.
Taking geometry as a great example , even if I generated a Mesh entirely procedurally from code, if I then wanted to attach a material with a bunch of parameters to it, I would not need to code creation of a new SpatialMaterial and write out assigning each parameter in code. I would instead prototype the material in the editor/inspector, save it as a resource, then only set the generated Mesh's material in code in 1 line.
You CAN, do it all in code if you so choose. The entire API is documented to support this and hell, the source code is open if you wanted to get down to that level. But the engine/docs aren't somehow wrong for not promoting this as the best way.... because it isn't.
