If nothing is selected, moving a tick mark should shift all tick marks at or after the current time. Tick marks at earlier times should stack up (when moving the tick mark to the left).
If an object is selected, the behavior should be the same, except that only the tick marks for the selected object should be modified.
If nothing is selected, moving a tick mark should shift all tick marks at or after the current time. Tick marks at earlier times should stack up (when moving the tick mark to the left).
If an object is selected, the behavior should be the same, except that only the tick marks for the selected object should be modified.