There are cases where a batch macro is used for multiple tasks where not all of the control parameter inputs are available all of the time. To use a batch macro control parameter it must be populated with a field, meaning sometimes a field containing a dummy value may have to be created to work-around this forced populating.
It would be useful if control parameter inputs could be made optional, passing a NULL value when a field hasn't been provided and handling any NULLs passed in within the batch macro.