Gen 2 Dataflow unable to use other dataflow source

Hi Lorenz33, 

As Murtaza_Ghafoor suggested, what I would recommend is have your first dataflow write to a lakehouse/warehouse, and then have your second dataflow pull from that lakehouse/warehouse.

Dataflow Gen 2 works differently than dataflow Gen 1. Gen 1 acted as a data store for you to use in other queries/reports, however gen 2 is designed for data movement/transformation, not as data storage, so having your first data flow store the data in a lakehouse/warehouse puts it in a place that is easily accessible from the rest of the Fabric platform. 

Here are the docs on adding destinations in dataflow gen 2: Dataflow Gen2 data destinations and managed settings - Microsoft Fabric | Microsoft Learn