Conscious thought requires a delicate interplay of neurons and chemicals, that if disturbed by visiting a permutation of the multiverse, would cease to function.

Humans can not directly observe an alternative permutation, but even if they could, how would they be able to find their way back to their original permutation if there's an infinite number of permutations?

"Conscious thought requires a delicate interplay of neurons and chemicals, that if disturbed by visiting a permutation of the multiverse, would cease to function."

The multiverse need not have different physical laws; the quantum multiverse if true, for example, is basically our universe just viewed from a different point of view.

"Humans can not directly observe an alternative permutation, but even if they could, how would they be able to find their way back to their original permutation if there's an infinite number of permutations?"

Unsurprisingly, science fiction authors have pondered this for a while, and one popular answer is a travel machine where part of it still stays in the universe of origin, so returning home is like pulling a rope back in. Even if we're in a quantum multiverse where the source universe and the destination universe are continuing to fuzz, you can still imagine there's some sort of correspondance that means that any given individual will still have a uniquely-corresponded universe to travel home to.

I believe this is all technobabble bunk since I doubt it can correspond to any possible real configuration of atoms and energy, but, like I said, someone could well prove me wrong by building one, and that would be that.

If every action that can happen, does happen, then the "universe" that you left only exists in that exact moment of departure because every quantum interaction from that point forward creates more branches of infinite universes. Thus, which of those would you return to? You could only return to the exact moment you left or to some random branch that's created after you leave.

Maybe you can just observe something coming out of an alternative universe into yours.

Maybe you could go in an alternative universe that is different, but not different enough that it prevents you to function.

The absence of observing someone or some object to date suggests that multiverse can not be observed or can not exist, because if it was possible to observe or if it did exist we would have seen some evidence of it by now.

In an infinite universe, there should be constant evidence of multiverse apparent.

In an infinite universe, there are an infinite number of variation of universes with properties implying any given of event happen 0, once, rarely or often.

That's the problem with the infinite universes theory. You can pretty much make up whatever you want, it answers to any question.