How to report on subform variables

How to report on subform variables

Hi!

I have an "order" form which includes an "order details" subform. 
 
The fields in the "order" form include

  • Order_Number (num)
  • Customer_Name (name) 
  • Order_Date (date)

The fields in the "order details" subform include:

  • product_name (integration - lookup from CRM products)
  • product_category (text)  
  • quantity (num)
  • customer_price (num)
  • earnings (num)
 I want to create a stacked bar report that shows the sum total earnings from the subform, stacked (grouped) by product_category also on the subform,  listed by date (month) from the "Order Form".  

However, I have been unable to access any of the fields in the "Order Details" subform in the report column menu, nor the Order_Details subform itself.

According to the following link  https://www.zoho.com/creator/help/forms/creating-subforms.html#Creating_a_Subform I should be able to access the subform fields in the report. But perhaps this has been changed (removed) in Creator 5?