https://www.punctuationmatters.com/en-dash-em-dash-hyphen/
I didn't even know there was an "en dash" or "em dash". I just assumed varying hyphen lengths were down to font choices. So this is an education. From the examples in the article it looks like I've probably been using commas where an em dash would go.
Now I just have to figure out how to generate them on my keyboard.