What is the term for conjoined twin separation?

I couldn’t locate a name either, other than “separation surgery”.

Dissection surgery?

Not dissection, that’s the term for a procedure similar to an autopsy, only on another species.

Since you brought up dissection, perhaps bisection may be more fitting?

Presidential candidate Ben Carson is famous for being the first to separate occipital craniopagus twins. I haven’t seen a term for that whole procedure, though, besides ‘separation’. It was complicated