Hi,
I'm afraid not. Anyway, not by standard means. Correct FM flow presumes adopting FM assignment through the document chain. Reassignment of the whole chain would be required in case of modification, but even this won't assure you a split of the document.
Regards,
Eli
P.S. However, check note 1963220 - Enhancement of FM Derivation Tool and 1875038 - Enhancement of FM Derivation Toolfor better control on derivation of FM assignment in the chain.