Well, as you write, I will implement the feature when saving as standard MIDI file to show message box to select whether apply or not track's time+ / key+ / vel+ to the events if their value is changed like track's channel in the future's version.
On the other hand, I think it is a bit difficult to add applying track's time+ / key+ / vel+ check button to the modify event's time / key / velocity dialog. Because the edit dialog applies only to the selected event, so if track's time+ / key+ / vel+ is remained, the selected events are double moved, and if track's time+ / key+ / vel+ is reseted to 0, the unselected events aren't moved. Maybe it's a bit confusing for beginners. But I consider to add the check box if it is useful in the future's version.