Hi @CPU,
Welcome to the Auth0 Community!
I understand that you have encountered issues when trying to update the change_password email template using the Management API.
After testing this myself, I found the same observations as you. The change_password and password_reset email templates are tagged as legacy and are meant only for legacy tenants.
In this case, I believe the correct email template you are looking for is labeled reset_email. I can confirm that this email template produces the Change Password email template found in the Auth0 Dashboard.
I hope this helps!
Please let me know if there’s anything else I can do to help.
Thank you.