As of 1.69.0, you can now update the password hash using the User API.
From the documentation, the passwordFieldType is the API field to use. This field:
Describes what user.password in the request is. The possible values are:
HASHED - user.password is an already hashed value. When this value is supplied, user.encryptionScheme, user.factor, user.password, and user.salt are required.
PLAINTEXT - user.password is a plain text/unhashed value. FusionAuth will hash this value according to user.encryptionScheme and user.factor.
