Bobby,
My understanding is that Wolle is actually trying to export a displaceable object:
Wolle: "[My question is this: How can I populate self edited Stones (i.e spheres,cubes etc with PF as surface shader)?"
You're right that this is not synonymous with a fake stone (my error in definition) but Wolle clarifies what he wishes to do again:
Wolle "In TG I load a displaceable object (sphere, cube etc), add object/displaceable/sphere. Now, this object is transformrd into a decent Stone (PF3, 2 colours) see attached Picture."
Will the method I described not achieve the above intention? i.e. create a stone via displaceable object, export and reimport as population, stick on a surface shader and the deal is done. I am very new to Terragen so apologies if I'm completely wrong.