Indexing parallel universes / labeling.

So i’m making this universe generator, and i label each galaxy/star system/planet based off their coordinates which are calculated in relation to known pulsars/galactic center/main star(s). It got me thinking, how should i label other universes? What should be the point of reference? There is no “main” universe, there is no continuity either. They just exist. Any thoughts?

if every universe contains the same dimensions, the multiverse should be unbounded centered around the center of mass of all universes.

if they just exist they should be called “this”.

Hmm so there could be a “galaxy” of universes… all rotating around the center of mass. Or will they be rotating? Now we are moving to sci-fi, so lets say yes.
Will different universes have different properties? What are those properties? Maybe some universes express presence in other universes in some weird way? Maybe that could be used for calculating “position”, just like we define a position of a galaxy based on the distance to known pulsars? I think i will expand this more and use it as a explanation for the position of the universe in the universe map.