It is in the same application context. For example the data type is defined as class Sales-Data-OrderType. The application class group where the case type resides is Sales-OrderMgmt-Work-Order. I can see "Order Type" in the class browser. I can see "Order" in the Case browser. According to all the training I should be able to edit a step on one step of a stage in the "Order" and on the "Configure Form" screen I should see "Order Type" when I click on "Data Types". However nothing ever shows up in the "Data Types" section. This leaves me unable to setup "Data References".
I confirmed this is due to the fact I am using Pega 7 Personal Edition- I just created another application and got the same result. However I tried the same test on an On Premises installation of Pega 7 and it worked as expected. I haven't yet discovered a way to get this feedback to the Pega 7 PE development team
In the class for your data type (go to the Data Explorer, and select View definition from the contextual menu) select the Automatically generate a unique ID for records of this type check box.
Also, open your data type and on the Records tab ensure that you have configured a source for the data type (most likely local data storage). I believe that these two changes together will allow Case Designer to pick up your data type when you open Form Builder.