In most of these cases, you will not need to extend a Composite Node. By "most of these cases", I mean that you can create very complex AI Behavior Trees that can perform very complicated tasks, and that you really shouldn't extend or create a Composite Node unless you really need to.
In fact, a Composite Node influences the flow of the Behavior Tree, including which node to execute, which Decorators to check, and which Service to activate. By default, there are only three: Selector, Sequence, and Simple Parallel. These will be more than enough for covering most of our cases.
However, if you really have specific needs, then Unreal Engine is so flexible that it allows you to extend a Composite Node as well.
First of all, this is impossible to do in Blueprint, so the only way you can extend a (or create a new) Composite Node is through C...
