SYMPTOM:
When manually adding a Value Prompt in the Derived Metric formula definition with the following notation ? then clicking on the Validate button, the following informative message is seen:
Object (of type: Prompt) not allowed in this place.
CAUSE
This is working as designed; currently, it is not supported the usage of Prompt objects in the derived metric formula definition.
ALTERNATE SOLUTION
1) As a workaround create a regular metric containing only a Value Prompt as its definition; for instance:
2) Add the newly created metric in the report definition.
3) Thus, this metric will be available to be selected in the derived metric formula definition.
