Hmmm. i don't know. If I remember correctly trying to add a second set of lights ends up replacing the first set.

You could try adding just the lights to a scene and saving it as a .pz3 file.  Create another new scene and do the same thing.

Then use "File"and "Import" to bring in the first scene with lights so that they combine with the second scene and it's lights.

Don't know if it will work, but it's worth a try.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi