Custom EditorScript for array?

I'm trying to create a customeditor script for an component represented in a list.

Let me outline the problem:

Waypoint (MonoBehavior) has many Directions (Normal serializable class)

I can create my own customeditor script for the Waypoint component. The waypoint component consist of multiple Direction components, which I want to be able to create a customeditor, so when you unfold the list, each object is represented by my customeditor script.

Hope some understands and can help :)