I found the appearance. 🙂
I don't think that they are actually holding hands like it was put there, but it's mostly just a metaphor, a symbol of balance between them and the effect it has on creation, it's how the Phantom Stranger and Etrigan percieve that.
I am reconsidering the relationship between Yahweh and Light/Darkness, since it is possible that the conclusion I arrived at reading only the main-arc was incorrect.