Re: Experimental version - 0.8.25
Stopwatch in countdown mode within the segment prior to the synchronization point should work. However the countdown mode only works if the stopwatch has a well defined range, specified by start and end points.
I think in your case you want to do the following:
Go to the begining of the segment.
Add the stopwatch object on the first frame.
Right click the stopwatch and choose "Start"
Move forward in time up to the synchronization point (shortcut: F8).
Right click the stopwatch and choose "Stop".
Right click the stopwatch again and choose "Countdown".