Just make a set that only switches your trinket and then make a macro which swaps between the two trinket sets (you can call the required functions in ClosetGnome via script commands in a macro) by doing something like "if set1 is equipped then equip set2 else equip set1". That should do the same thing.
This page has the script commands you'll need to use in the macro:
http://www.wowace.com/wiki/ClosetGnome