Replace the Python Window in ArcGIS Pro with Python Notebook.
if you mean the jupyter notebook Project Jupyter | Home
it is coming since upcoming versions are going to be anaconda distributed which contains both ipython and jupyter
Anaconda package list | Continuum Analytics: Documentation
more links here Coming to Python.... preparation and anticipation
and the arcgis api for python ArcGIS API for Python | ArcGIS for Developers which supports jupyter
Retrieving data ...