Virtual DataPort provides "View Parameters" to parameterize the input values.I would define the View Parameter such that it does not contain any default value. This way, before executing the view, I will be prompted to provide the value for the View Parameter.
However, Tableau introspecting this view will throw an error which is expected. You could write a custom SQL on Tableau to ensure the paramterized field is always supplied with value to overcome the error.
You could request Tableau Community for integrating the view parameter natively through the Denodo Connector.
Hope this helps!