./widen-exporter mapping --token="dummy/somerandomgeneratedtoken" --filename="yourfilename.csv"
./widen-exporter metadata --token="dummy/somerandomgeneratedtoken" --filename="yourfilename.csv" --query="ff:{PDF}" metadata_field_1 metadata_field_2 metadata_custom_3
You can get the query string from Advanced Search in Widen UI. All metadata fields will be the machinename of metadata fields.