What do you mean export it? Like from the Connect website to your 820? That's absolutely possible.

I think the screen will change to a workout screen (and your field customization won't be visible, it's like a new data page) and you'll get stuff like a timer for the current step.

When you set this up, you had the option to set a duration (10 minutes, etc) or to end that step with a press of the lap button. You opted for time, so you won't have to press lap.

Personally, I don't use the workout feature. I can achieve everything with a data page that shows time in the current lap and other stuff like my HR or power. When I do hill repeats I hit lap at the bottom of the hill; for other types of workouts I might hit lap based on time or some other target. But in any case I just do it manually.