This is a small breakdown of the menu select skips used for NG+ and rough estimates for how much time they save. I just did some very cursory timing comparisons with some pretty mediocre menuing.

The skips are all done the same way with hacker into fall being slightly different for when you exit the level. hacker into fall: Exit the level when punching yourself in the head, use level select to enter fall. all other skips: Exit the level when the last dude shatters, use level select to enter the next level.

subway into jump: Saves roughly 8 seconds. tiralley into server: Saves roughly 25 seconds. server into dog1: Saves roughly 8 seconds. hacker into fall: Saves a whopping 2 minutes and 15 seconds. office into station: Saves roughly 25 seconds. station into train: Saves roughly 8 seconds. train into gate: Saves roughly 8 seconds. gate into lobby: Saves roughly 8 seconds. lobby into longway: Didn't time it, but it's probably not worth it. With good menuing it's probably like 2 seconds at most. longway into core: Didn't time it or check if it's possible, but I would guess roughly 6 or so seconds if it does work.