Currently there is no way to copy a mapping within the same ETL set in Compose. The only way around this would be to duplicate the ETL set. Being able to copy a mapping within the same ETL set would eliminate the need to manually recreate the map when most of the logic remains the same. For example, an ETL set that has identical mappings but has different filters (e.g. on a different date field in each map). This seems like a very minor lift and I am surprised it isn't an available functionality.