See widgets without having the notebook open

[hbcarlos]

Description

As it is right now, we need to have the original notebook open to see the widgets. This is related to not having a kernel session open.

Solution

The solution adopted on Voila-gridstack consists of registering the dashboard widget in the document manager as if it were a new DocumentWidget for a notebook. This allows keeping track of the notebook state by using as a DocumentModel the NotebookModel which is the class that implements the state of a Notebook in JupyterLab.

This solution makes complicate to work with outputs from two notebooks in the same dashboard. Besides, when cloning an output from the notebook to the dashboard if this output has a widget, it's necessary to register this widget into the widget manager and treat it as a new widget.