Parameterize field mapping helps you to make the mapping dynamic.
This will be helpful in a scenario where you want to use different connections(source or target) at run time.
Eg: If you are using a relational connection and which has tables with different structure and you want to load data into different target tables(with different structure or field name) then parametrize field mapping helps in making it possible where you can define the field mapping at MCT level.
Thanks for the udpate , I have started testing the same but while creating the parameterized target connection in the mapping it is throwing an error saying at least one field need to be mapped. How to avoid this issue. do we need to keep the target also full parameterized value ?
Please set Automap instead of manual field mapping at the Target level.Your mapping would be validated.