The Google Cloud docs have an interesting placeholder implementation.
Users can click on the placeholder instances to turn them into the corresponding input box, so they can be updated in-place.

EXAMPLE PAGE: https://cloud.google.com/kubernetes-engine/docs/how-to/api-server-authentication#applications_in_other_environments

Step 1 - Default

Step 2 - Click to edit

Step 3 - Changes are reflected across page

They also have real-time mutation, but that is not necessary.