Because samples libraries often have variable delay times PER articulation... ie a spiccato articulation might be delayed by 40ms from the onset of the sample to the impulse of the attack, but a legato articulation might have a delay up to 100's of ms... but both exist on the same track (especially now with sound variations!), we need to be able to set individual negative offsets per event. You already have transpose and velocity in the event inspector... just add delay / advance.