Thank you so much for the quick update!
Plotting with PythonPlot works now!
Zoom and pan work, too!
Small issue: Clicking the “Fit to window” button never enlarges the figure beyond 100%. So it works only if the window is smaller than the figure.
You need to call figure() to create a new figure, but I think this is normal. Perhaps figure() should be called automatically when the “Clear” button is clicked.