May be repeating what’s been said, but I have only been able to see the bars on Garmin Connect post-workout. During the workout I have my Garmin 1030 screen set like this : you could have a lap av power field if that helps you keep focused on the interval av power target.
My Garmin also gives me audio cues (countdown from 5 sec) for target changes. Don’t recall where to find that setting.