That’s not how datahub works AFAIK.

Datahub provides a catalog of available data that can be easily used in your model and keeps track of the relationships between the catalog of services and the consumers.

The connection between a selected service and your app consuming the service is direct. So if service customers from app X is published in datahub and used in Mendix app A the data flows from app X to A directly.

Currently there is no diect way to write data back, this should be implemented seperately in the app A and app X should provide the service of course (apps from the example above)