A stored function is a set of statements that can be stored in the server. Once this has been done, clients don't need to keep reissuing the individual statements but can refer to the stored procedure instead.
Database Designer for PostgreSQL helps to build and manage stored procedures and functions in a powerful graphical environment.
With Database Designer for PostgreSQL you can:
§Create and Edit stored procedure or function;
§Manage all stored procedures and functions within the diagram.
See also:
Creating a Stored Procedure or Function | Stored Routine Editor | Stored Routine Manager