The Getting Started Guide ("CHAPTER 4. TEST SCENARIOS") mentions "2. iv. Click Test Scenario to open the Create new Test Scenario dialog....... Click the Choose DMN asset text field and select the path..." in the "4.1. Testing the traffic violations using test scenarios" section.

However the widget/component should probably be more correctly described as "Click the Choose DMN asset list and select the path..." This would also align with the terminology used for the "Package list" in "2.ii. From the Package list..."