If you forget to stop/restart the transcription between patients and end up with a 40 minute transcript for 2 different patients, it would be helpful to be able to place a marker in the transcript in order to split them into separate sets of notes. This might also be helpful/save time for consultations where an owner brings 2 or more pets in and it all gets lumped into the same recording. Situations sometimes also occur where an unrelated phone call (regarding a different patient) is mistakenly incorporated into the previous consult's notes because the transcript wasn't stopped.
These are all avoidable situations, but they definitely happen regularly enough that it would justify a feature to "exclude everything after this point in the transcript" or "split into 2+ sets of notes at this/these points".