Not really, there’s sort of two types of multiverses. There are multiverses where the universes are separate but similar things and multiverses where branching timelines create new universes (and disgustingly ones that intermingle the two and muddy the concepts). If you’re writing about a specific universe in a multiverse that doesn’t strictly use the timeline branching model and you change things then you’re no longer “canon”.

Big quotes around canon because obviously fan made stuff isn’t canon, I just mean in the shower thought sense.