How do I add a new classifier, filter, kernel, etc.?

As of WEKA 3.4.4, all the derived classes of superclasses that can be edited in the GenericObjectEditor, like subclasses of weka.classifiers.Classifier for instance, can be determined dynamically at runtime. Read here for more information.

Note: WEKA 3.5.8 and 3.6.0 turned the automatic discovery off by default. Starting with 3.6.1 and 3.7.0 it is turned on again.