Hello Augustine,
There isn't currently a native means within the CODM to make a switch (stop/coupler/tremulant) change state automatically to the opposite state of another, I'm afraid.
Here are some other recent topics that discuss that (or similar things), in case any of the work-arounds that people have tried might be of any use to you:
viewtopic.php?f=13&t=18516
viewtopic.php?f=13&t=18877
viewtopic.php?f=13&t=18750
(E.g. perhaps you could do it with duplicated ranks, using 'tremmed/untremmed' switches to switch each between real pipe samples and silent samples, or something along those lines. However, I'll have to leave that to you if you want to try that.)