Writing is definitely better, but I wonder, is it the endpoint? Has anyone had much success with argument mapping tools, or other alternative ways of expressing reasoning and evidence?

That's an excellent question. I haven't, but would be interested in exploring this if you have a preferred tool.

I've gotten some benefit when talking about complex issues from introducing formalisms such as labeling key entities and using those labels rather than vague pronouns, or being precise about "there exists an X" vs "for all X", and stuff like that. That said, there are signalling difficulties with doing that in most communities.