Sorry I cannot point you to more precise details. Maybe someone else will have a better idea? …
My understanding is Jupyter Notebook 7+ is built on JupyterLab components and JupyterLab has traditionally not been as directly modifiable as the old notebook (v6.4 and earlier) interface. See here for an related discussion that I think brings up in a different way:
“As an explicit design choice, there are no stock lumino layouts that will create an independently draggable window. Part of this is that it demands a whole separate layer of concerns for keyboard navigation and window layout restoring.
However, an extension has full access to do whatever it needs to the underlying DOM, and as such could basically whatever is needed.”
This reply is mainly my long way of saying to make sure you are looking into resources related to Jupyter Notebook 7+ when trying to understand what you need to do to achieve your goal. There’s a lot out there on the internet for the older notebook interface that doesn’t apply.