Adjust the start time of a note's playback
Sibelius calls it "live start time". The ability to change when the playback of a note begins in relation to when it is triggered as the score is read. Just as you can adjust a single note's velocity in the inspector, you should be able to adjust the note's start time too.
Take grace notes for example. It seems as if everyone has a different interpretation of when and how a grace note is played. With this feature you could change the audible space between the grace note and the note it is attached to. Or you could place the grace note on the beat and the actual note slightly after the beat. etc. etc. Another example would be the triggering of long samples, say your soundfont has a suspended cymbal roll sound, but the cymbal breaks a little too early. You can simply change when the sound is triggered to achieve the desired effect.
I understand that both of these things can be achieved by having the written notes not produce sound, write the desired effect in voice 2, and make voice 2 invisible. While this works, the process is cumbersome and can quickly clutter a score if you use the technique frequently.
Comments
The interface that is intended for this is the Piano Roll editor - right-click bring up the menu to display it. In reality, it's pretty fiddly, but anyhow, that is the feature that allows this. There are reasons it isn't in the Inspector - consider, some notes actually may produce multiple events (trills etc) and you will possibly want independent control of them.