@JCHollett thanks for your response. To be clear I prefer to stay away from overriding keybindings as users may define their own bindings and then those don’t get handled by the overrides. So instead I would prefer some kind of hook I guess.
I also do see transactions in the my plugins state.apply but unfortunately it does not seems clear from it when split was attempted. I also hoped that schema somehow guides how nodes / marks are split.