[World Editor] Importing new SpeedTree models?

I cannot get any new SpeedTree models into the Multiverse World Editor, after trying many ways. I've tried using the COLLADA importer and the Asset Importer in various ways, but never with any results.

Does anyone know how to import new SpeedTree files?

AFAIK, if you still have the older version of SpeedTree which means the same version as the examples included you can use it without any problems.