Splitting is not currently considered an accurate term in DID, since splitting is a term used in psychiatry to describe the inability to hold opposing thoughts, feelings, or beliefs. This is seen in C-PTSD when someone can only consider extremes, aka "black and white thinking". For this, check out The problem with extremes.
If you mean splitting as in some of older ideas about formation of headmates, see alters. Some folk in the community do experience themselves as having split in the past, or splitting off new headmates.
There's also a a review of the movie Split New.