Hi! I'm not sure I understand you well; do you want to be able to use an arbitrary .pln file in the material preview inside the material editor? Note that there are multiple shapes for this object, and you can also rotate it, adjust its radius and/or the light intensity. The main light used in the preview is pure white, with another smaller light with a slight blue tint.
You can also preview the edited material directly in your scene, if you start interactive rendering before you open the material editor. (Unfortunately, due to some technical issues, you cannot start interactive rendering when the material editor is already opened.)