It should be suspend the program. After suspension, no breaks shall pop-up and
the timers shall make no progress. Suspension could be controlled GUI-wise by
means of a new entry "Suspended" in the pop-up menu, which can be checked and
unchecked.

Done. I think this needs more visual feedback. Some kind of red cross ???

I am not sure I am satisfied with the current approach. Personally, I would use
suspension when, for example, when a customer comes by and wants to see a demo.
In that case, I am quite active behind the computer, but I do not want to be
disturbed by WR. That part is now covered. What is not covered is that when the
customer leaves and I unsuspend the program, the program should either do one of
a) continue in the exact state from before the suspension (suspend is actually a
time freeze)
b) all activity in the suspended state is accounted for, and the program
immediately tells me to take a rest break if the demo took long enough (suspend
is actually a "quiet" mode)

IMHO, a) does not really make sense... b) is the desired behaviour. Therefore,
the menu option should be renamed to "Quiet", and the suspension behaviour
should change accordingly.

I think "suspended" and "quiet" are two different features. "Suspended" is
useful when someone is highjacking your computer. During that time, workrave
should not count any active time. I don't want to replace "suspended" with
"quite". But I agree that option b) is also required

Quiet added. Ok?