Codebeamer - project configuration to define what tracker may be upstream/downstream from another

Hello, and thanks for your question.

In a tracker's Configuration settings, on the Fields tab, you use choice fields to define the allowed upstream reference relationships for work items in that tracker. 

As shown in the image above, the Datasource for such a choice field is Work/Config Items.

And below, you can see an example of the reference definitions for an existing choice-type field with a Work/Config Items datasource:

The section of the Codebeamer User's Guide that covers this subject is Creating and Customizing Trackers, specifically Reference Fields and Trackers Reference Fields.

This is indeed an advanced administration topic, which our course offerings do not yet cover. However, we hope you find the above information a useful starting point.

Another suggestion for learning how choice fields (specifically, those choice fields that are also referred to in the documentation as "reference fields") is to examine the settings for those choice-type fields in a tracker, and then observe how those reference settings are reflected on the project's configuration diagram.