Technical issue, resolved
Technical issue: Upon trying to save the previous draft, the New post page produced a line of text telling me that I must "Enter a valid 'slug' consisting of letters, numbers, underscores or hyphens."
No clue as to what a "slug" means in this context, or where I need to put it. But I'm persistent, and have discovered that this particular 'slug' has to do with the "Permalink" field.