A way to stop it from adding new characters

Maybe this exists already and I've missed it, but a way to stop "it" (A.I. thingie) from adding new characters. Yes, I tried plain english like: "Do not add new characters" and it still did. Well, except for the "casual characters encountered along a journey" so to speak, those are fine and good. But characters from whole cloth, no thank you. Sudowrite is still cool and amazing, and this is just my feedback.