Extending Sverchok - Development of new nodes in a separate addon TL;DR: Is Sverchok designed to have their node list extended by third-party addons? If so, are there any formal templates to follow?
I would like to play with the idea of developing new nodes for Sverchok in a separate addon to provide domain-specific functionality that would not make sense to be contributed to Sverchok itself (e.g. generating meshes to be exported to third-party software). My understanding so far is that this would be a two step process:

Create the nodes. This seems to be well documented in Sverchok, and the many nodes included provide many examples of varying complexity.
Add the nodes to the menu. This is the bit that I am struggling with. I have not found documentation / example templates to this end, hence the question. There is sverchok-extra and this file seems to make nodes available in Sverchok's menu. Would this be the way to go?

I am aware of the custom nodes one can create in Sverchok itself via scripted nodes, but it does not feel the right way to develop an addon that saves the specific nodes and makes them available in the menus for future, easy reuse.
Thank you.
look at ladybug addon for sverchok and even more to sverchok extended nodes addon
https://github.com/nortikin/sverchok/wiki/Dependencies#side-extending-packages
also. But make an issue on nortikin/sverchok for that to proper integration