Hi.

It can be saved with the scene or picked up. I (think) I tried it both ways, no joy.

I also tried copying the file out to the same (realtive) place on the render nodes.

It is possible that they only work in some default folder within "program files".

So there is room for my conclusion being wrong. However my experiments all proved fruitless.

Please feel free to have a go and report back. That would be great!

I have a tutorial on creating IES lights (with free software), so you can create definitions that are very different from the default one.