On the tree node for greenplum datatypes you can multiselect datatypes and script create/drop.  If we can't script the objects one at a time, guessing we shouldn't script them with multiselect, plus the script create is not proper DDL syntax but the drop is, so the object will drop and then wont recreate from the generated ddls.  example:  CREATE TYPE "ivan"."ivanbox" AS (f1 int, f2 text);

  select 2 objects and script drop/create and you get this for "ivan"."ivanbox"

DROP TYPE "ivan"."ivanbox"

GO

CREATE TYPE "ivan"."ivanbox" ( INPUT=record_in, OUTPUT=record_out, 

    INTERNALLENGTH=VARIABLE, EXTERNALLENGTH=VARIABLE, 

    DELIMITER=',', 

    ALIGNMENT=double, STORAGE=extended )

GO

  The drop will correctly drop the object but the create will fail...