Actually, Tubes shouldn't be in any section until they add the 2D section they're talking about adding. Tubes are not "Just for Poser" nor are they Plugin's which is a term for Software code that adds functionality to a program.

The closest section they fit in for now would be either Textures or Materials as they're usually used as textures on a square prop inside a 3D program in place of an actual mesh of an item.

It is a miracle that curiosity survives formal education. - Albert Einstein