Thanks for your interest in improving Matplotlib!

That type of chart is super-specialized and I would expect better suited to an external library. We don't provide a tree plot, either, though https://github.com/erdogant/treeplot does. If the external library proved popular, and/or there was a compelling reason it needed to be in core, it would certainly be possible to consider.

This could also maybe be a gallery entry at https://networkx.org/documentation/stable/auto_examples/index.html but you'd have to ask the networkx folk

Think about this more, it is definitely something that should be developed elsewhere. The API for this will be extremely broad, so best to refine it first. Please feel free to approach us again if there is a package that should be subsumed, or if it is not possible to make what you want without changing Matplotlib internals.

Thank you @jklymak for the support. I will try to ask the same to some dedicated projects or I will implement it for specific cases little by little.
Regards,
Robert

PS: For one that will read the post in the future, I have implemented only the Ishikawa plot from scratch by using only matplotlib and numpy.
You can find the code here: fishbone diagram using Python or graphviz

Great! Your s/o post seems modest sized so consider adding to our examples?