You will only be able to edit the last message that Franz sent, because older messages are already baked into the summary.
You can use this command to edit Franz's last message when he said something wrong or you want to steer him in a different direction.
You can access this command by right clicking his last message and selecting
Edit Franz under the
A modal will pop up with a text box to enter the message you want Franz to say.
Submit the message & Franz will edit his last message to say what you entered.