Ah, yeah, I am very happy that you got error messages working, it must have been so difficult to try and work out what was going wrong. I've tried to put in a decent amount of error checking, but it is also something I want to improve going forward.

I think if there's one good thing that comes of your struggles to get it to work, it is that I've realized I should be a lot clear about this in the documentation, and I will really improve this section, including screenshot of what is expected to show on screen and how to deal with errors!

Making a GUI or editor is something I've been thinking about (likely as a standalone Yarnspin Studio), but to be  honest, it is not something I have in my plans for anywhere soon. I have a lot of ideas for features to add to Yarnspin going forward, and having to maintain a visual tool for it will just make those much harder and more time-consuming, and I don't want to be slowed down like that. But I do think it would be a fun thing to make and a useful thing to have,  so I could see myself tackling it some day.

But hey, since this is free open source software, we can always hope that someone else decides they can't wait and starts making one - not very likely maybe, but we can hope :)