I like to manage keycloak from my own application:create user & clients, display users & client. As this is not a real user but a machine I would like to use a service a
Keycloak differentiates between the Scopes/Scope mapping & the roles management.
The Scopes tab: you see in the question above only manages the roles that a client is allowed to request.
For the client credential grant to work these roles must be assigned to the client in the "Service Account Roles" Tab.
So in the end the client receive a token that is the intersection of both of those configurations.
Source: https://www.keycloak.org/docs/latest/server_admin/index.html#_service_accounts