@kirchner, I realize it has been a few months since your initial post. @Krolich created a document to answer some questions you asked and you said (in response to the document that @Krolich put together):
Thank you for your feedback! A document with some insights would be very great if you can afford the time. 
It does not have to capture the whole thing, if that is too long. We probably want to do some iterations over it anyway, i think.
Several forum members posted ideas and you said THIS:
You are right! As for moving forward: I will be thinking about all your feedback in the next week and will try to come up with some a bit more detailed feature list and some workflow descriptions. (Iāll probably put it on github.) Perhaps further discussion can be done there? I donāt want to spam this forum, since I understand that it is meant for discussion around the Seamly-tools!
I do not mean to be a nag, and I realize that priorities can change. That said, there is renewed interest in your effort and the time may be right to collaborate. I am writing this message because I am willing to personally write some code if needed and I believe there is very little that would be needed to get you to a point where you could open a Seamly created pattern file and display it. I had forgotten about the already existing ability to use Seamly from a command line and the comments made by @MrDoo in this thread point out what can be done.
Using the ā*.valā file as an API MrDoo was able to create a powerful tool with almost no code. He has added one feature that is not available (and probably needs to be added) in Seamly2D. That feature is that instead of crashing if fed an incomplete set of measurements, the seamly.cloud will allow the user to enter missing measurements.
I imagine a simple process that you could do to āloadā a pattern and measurement file into the environment that you created at elm-pat and use your existing interface to make minor edits - moving points, etc.
There are still many issues that will arise because of the different approach: elm-pat does not seem to require any sort of hierchy. It appears to me that a user can create points independent of each other. Seamly2d starts with ONE base point and every subsequent point is drawn relative to that through a sequence of formulas.
I believe it is a worthwhile exercise to load a pattern file into āelm-patā and tinker with it, and I am willing to assist. It is possible that @MrDoo would be available to answer questions about how he did what he did. What about it, @kirchner, would you like to proceed or has the time for this collaboration passed?
Regarding the concern about āspammingā the forum, I believe that in the past users have been asked to keep comments to the original thread or to start a new thread. The good thing about a āthreadedā discussion is that folks who are uninterested in a topic can simply avoid reading it. This thread started to discuss elm-pat, and I believe I am proposing that you can (if you have time and inclination) add a capability to elm-pat that would help you clarify what you want to build while at the same time providing a useful tool for some who have asked for some Seamly2D enhancements