I think if reincarnation was/is real it’d probably work regardless of time and creatures would be locked into their own categories. So like, humans could only reincarnate as other humans, for example.
When I say it’d work regardless of time, I mean like, if you died you could reincarnate as someone in the future or the past.
Kinda a silly discussion topic, but I thought it might be kinda interesting.
My guess would be some type of 4th dimensional movement. Consider the universe as we experience it as a 3rd dimensional face of a 4th dimensional polytope. If there was some wort of “soul essence” or whatever, it could exist as some sort of limited resource at a 4th dimensional level, flowing between different 3 dimensional faces in a manner impossible for us to track
I could see that, it’s hard for me to imagine, but I think that’s partially the point.