Well, then we just have to add more info to --help
+1 for at least doing that. I found it annoying just the other day not to find it in plsql's --help output, in a moment of brain fade when I forgot how to spell it. So it's not just beginners who can benefit, it's people like me whose memory occasionally goes awry.
No objection in principle, but what are we talking about exactly? Adding some new backslash command that lists all the variables that have special meanings?
That's a pretty good idea, especially if we give that command a command line option too, so something like