I would guess most, if not all, the edits were done on tape. Tape was not the medium of choice for making or archiving TV episodes (and Lucy herself was the pioneer of using film rather than live broadcast), but it was the medium of choice for distributing and broadcasting. My knowledge on the subject is tied to my interest in Doctor Who. Now that was made on PAL 1 inch tape. The first surviving episode in that medium is in the 7th season. Since the BBC distributed world wide to PAL, NTSC, and SECAM locations, they filmed the episodes and distributed film well into the 70's, but many of the recovered 70's episodes (and not many were lost) were recovered tapes. So sometime around 1974 the BBC (not known for adopting technology early) was distributing tapes. By the time TNG was being distributed, it was by satellite. As many stations airing TOS then aired TNG, I have always assumed that TOS had been distributed the same where. When that started I cannot say. From what the BBC was doing, a lot of the format depended both on what they offered and what the broadcast station needed. They had a considerable overlap of tape and film. It would have been easy for Paramount to make a master distribution copy on tape that was edited for time. It would also be easy for a station to get a film, transfer it to video and edit it for time (though time consuming). Some stations (as happened with Doctor Who) would have done it the old school way and edited the film. So I'm sure there was no consistent way that they were edited for time. The only thing I am certain of is that they were NOT done from the master negative, but from a distribution master that Paramount had. The master negative was not revisited until relatively recently.