How do you do triplet chords?
Make your chords as usual (all the same time duration, e.g. 1/8ths) by using CNTL Enter to add members or CNTL BS to remove them. Select the three chords to be tripletised and click the triplets button on the toolbar.
But once you have turned the group of notes into a triplet you can't edit the chord any more. You have to remove the triplet (or untripletize), edit the chord an then re-tripletize.