Additional datasource on loader

Please see my reply here: How to run below UIRunner code on additional datasource - #6 by krivopustov

In Jmix, each entity belongs to a single data store (main by default).
So when you load an entity using DataManager (which is used also by loader in view XML), it requests the data store of the entity. No other indication is needed, the entity is stored in the well known data store.