Currently, codex additions will add on to a codex entry, however over time or with significant changes, this can both confuse the AI, and isn't always compatible with all Codex entry structures (JSON is a good example).

Would like to have a flag so that rather than entering codex additions, they are instead codex replacements. That way, when the codex entry is brought in after that point, only the new entry is brought over.

This is useful when you have a character or other codex element that changes significantly between scenes or over the course of a story.