Overlay mode

WLJS Notebook App registers a global shortcut to provide an access to a new input cell. This floating input cell does not belong to any notebook, but works as normal one

You have a full access to any Cell types, you can even use it as a drawing board (see Markdown Excalidraw)

Or anything else you want

info

If the number of cells exceeds 3, it can be converted automatically to a normal notebook