The split button in the shader editor is missing. On the wiki it says there should be a button here but It isn't. https://docs.godotengine.org/en/stable/tutorials/editor/customizing_editor.html#splitting-the-script-or-shader-editor-to-its-own-window
Godot Engine documentation
Godot's interface lives in a single window by default. Since Godot 4.0, you can split several elements to separate windows to better make use of multi-monitor setups. Moving and resizing docks: Cli...