The definition of murder also doesn’t include a god killing another god.

which, nobody mentioned this far?.. you can’t make a claim and then attack it to justify your point. That is the definition of a strawman argument

If a god can not die at all, then telling a god that killing is bad because they wouldn’t want to be killed simply isn’t going to be meaningful.

So, according to you, this means an immortal god would not even understand why killing is bad? Sorry but I do not see the correlation here. Assuming your point for a moment, then none of the commandments hold any meaning to god since I cannot steal, harm or cheat an all-powerful entity.