I understand the idea of multidimensions is theoretical, but if they exist...
How are you using a keyboard as a 1-dimensional being? 😛
In all seriousness, I understand your question is more about alternate universes? In that case, I guess the term is Multiverse
Edit: Speaking of 1-dimensional beings, I just remembered a really cool video with Carl Sagan about dimensions, maybe it's interesting for somebody reading this!