Create new property on a node to store current position

I have a hierachy of Camera and Light nodes that I want to store their current x,y,z position before I alter them. So that I can restore them later.

So I want to create a new DzVec3 'property' to hold them.

But I can't seem to create a new property that lasts beyond the lifetime of my script.

Can someone please point me in the right direction.

--TromNek