More advanced tutorial on how to manipulate facetgrid

Is your feature request related to a problem? Please describe.
I have explored a bit the object returned by faceting a plot (usually identified like p in the tutorial).
It clearly stores tons of stuff that can be manipulated and make the plots more flexible.

I have an example here which I was planning to add somewhere to the tutorial for plotting.

Would this be of interest? or not since it makes use of i.e. matplotlib methods?

This issue is also intended to call for people that might have been playing with obscure attributes/method/whatever stored in p and have come out with some interesting manipulation. xarray faceting is very powerful, imho, and it is a great starting point for more complicated figures.

For example, in my notebook linked above, I add some axes to the side of the facetgrid to add a meridional average, and it used to take me a second to match the location of the added axes to the location of the axes in the faceted plot. But I figured that:

for oa in p.axes.flat:
    print(oa.get_position().bounds)

gets me the position.

I am sure tons of people have come up with similar stuff - so it would be amazing to put it all together in one spot!

Describe the solution you'd like
If there is interest, I will open a PR with an example on how to manipulate faceted plots.

Review the linked Advanced_plotting.ipynb alongside the xarray plotting tutorial. Start with the facetgrid object and the p.axes.flat example, then confirm with maintainers which manipulations belong in the tutorial. Done means an agreed, focused example is added to the plotting documentation.