And do you want to use the builtin graphing engine or do you want to use MatPlotLib?
Do you have a sketch of what you need and perhaps why you might need it and its purpose? There are a variety of graphing engines that are available in Pro.... some are better suited to certain tasks that others.
matplotlib is a python supported module (as is Seaborn and Orange both supplied with the anaconda distribution)....
This is first mention of ArcGIS Online. That is not ArcGIS Pro, so all bets are off. I have no clue if they use a graphing engine but I would venture, nothing that is builtin to the ArcGIS Pro distribution of python and its peripheral python graphing engines... maybe its builtin graphing? but I don't use it at all