I thought about this some time. How does the .j3o-format function? Is it just a scenegraph serialized? Could it be possible to serialize a custom mesh into .j3o-file? I know this probably is listed somewhere, but I’m not really good at searching information^^
Mesh implements Savable that is the basis of jme serialization.
It has a read an write method that implements its serialization.
So to answer your question, yes, custom mesh are serializable like any other mesh.
Or anything else implementing Saveable, (even your own custom classes if you do it right)