Basically that i can start the workout on the mobile and then keep track of my sets/reps/weights and pause timer on the watchOs app. The feature is rather 'simple' :
start training from the phone->
monitor current section . in normal exercise go set by set . Button starts set. after the set (button push) -> enter reps (show from plan if any) / enter weitghts (show from plan if any) -> after button push a pause timer is starting to check your rest (rest time not recorded-> maybe next feature)

for super set the mechanic is the same, just that the rest is after the last exercise ( so no rest between the exercises in a super set)

Design should be simple i want to train and not fill an excel sheet ;)