Bean Shell Form Binder allows you to dictate on how Form Data should be loaded and stored.
Sample Load Binder that will populate field with id "description" with the value "hello world".
import org.joget.apps.form.model.*;
FormRowSet f = new FormRowSet();
FormRow r1 = new FormRow();
r1.put("description", "hello world");
f.add(r1);
return f;