Credentials stay in this browser. They are sent only in request headers to HPE GreenLake and new Central (through a stateless pass-through that stores and logs nothing). Without credentials the page shows mock data.
Create the client in HPE GreenLake under Manage Workspace > Personal API clients and choose your new Central instance as the service. API clients scoped to the GreenLake platform (GLP) use a different token endpoint; for those, request a token yourself and use Bearer token sign-in.