online course Python interface problem

I accidentally pressed something while in the Python interface. And I cannot return to original view.
Please see question here.

https://drive.google.com/file/d/1PQqVAjU4kMkveI0_UGLFU6l5yPYJA69W/view?usp=sharing
thanks

You will have by now lost your notebook session, but basically you needed to execute the cell to return to the view of it that gives a clickable link.