To my knowledge the string builder data reference will evaluate the entire group of inputs and if a valid path will return the attribute value. In your case, you are trying to get the string builder data reference to evaluate individual inputs and then evaluate the group of inputs. I don't believe the string builder data reference supports this "double evaluation". Even if it did, this would be an expensive operation performed client side.
What's the data reference of the attribute \Equipment\TD001|Counter Value? If it is a PI Point, why not simply use substitution parameters in the configuration of this attribute and make it a PI Point? What's the use case of using a string builder data reference here?
Thank you it works.
In Template, I put the attribute as a PI Point and from an attribute. with value = \Equipment\%@|PC01_NAME%|Counter Value.
When an element is instancied, the path is built with the value of PC01_NAME and the value is taken.