Parameter Description: The QueryStringField2 parameter gives you the ability to add Conga Composer parameters into a separate Salesforce formula field, and then reference that custom field in the merge process. To reference that custom field in the merge process:
Creating a custom formula field on the object on which Composer is built.
Adding Composer parameters to the custom field as a formula, similar to what you do when creating a formula field for Conga Batch.
Referencing the API Name of the newly created formula field as the value of the QueryStringField parameter in the Composer button URL, as shown above.