For a complete list of available options, see database registration options.
For PostgreSQL, there are additional options available:
Additional Database Options
The username/password combination by default is the same as the server registration, but you can override it here or check the Prompt for password box so that Database Workbench will prompt you to enter a password every time you connect to the database.
The visible schemas list is used to filter the available schemas once connected to the database. Usually, you don't want to view the system generated schemas.