You are on the General tab. You can make the CompositeProvider available as a provider for other CompositeProviders by setting the This CompositeProvider can be added to another CompositeProvider flag.
This reusable CompositeProvider can then be used as the provider of a union operation.
If the CompositeProvider is already used in other CompositeProviders as a provider, you will see a where-used list and the relevant CompositeProviders are set to inactive when the CompositeProvider is activated.
InfoCube IC01 is used in CompositeProvider CP01, which is usable as a provider. CompositeProvider CP01 is added to CompositeProvider CP02. It is not possible to also add InfoCube IC01 to CompositeProvider CP02.