Need Overhange editable feature.

I research various terrain scene manager like Overhange Terrain, PLSM2,editable terrain,
then I found overhang editable not to have in PLSM2 or editable terrain.

If this feature can be considered into editable terrain or PLSM2, the terrain editable function will be perfect state.

As far as i know, ETM uses exclusivly heightmaps to represent the terrain data and with those you can't represent caves, overhangs and such. Since i have not read anything about moving to another approach i do not think ETM will support that feature now, or anytime soon, although i could be wrong there.

No, this is well beyond the scope of ETM/ETL. ETM concentrates on classical heightmapped terrain. If you need overhangs, you'll either need to do them via meshes placed on your terrain or stick to the overhang terrain manager.