Apple Soundtrack Pro 3 - Manual (Page 486)

Function Keyboard shortcut
Moves the Timeslice location to the previous frame.
option
Moves the Timeslice location to the next frame.
option
Extends the Timeslice to the previous edit.
shift
Extends the Timeslice to the next edit.
shift
Extends the Timeslice to the previous gridline.
shift
Extends the Timeslice to the next gridline.
shift
Extends the Timeslice to the previous frame.
shift option
Extends the Timeslice to the next frame.
shift option
486 Appendix A Soundtrack Pro Keyboard Shortcuts