notebooktag and search celltags in notebooks

[fbob]

First congratulations for this awesome plugin !
Many thanks :)
Do you think this plugin could be extented to have tags for an entire notebook and to be able to search tags within a predefined list of notebooks ?
A la Emacs org-mode (which has a very good jupyter-notebook support by the way) or Evernote.

Anyway many many thanks for jupyterlab-celltags !