It is possible to zoom in/out when building your workout. Especially when creating workouts based on a music playlist, it can be helpful to zoom in to see the details in order to time the music to the workout.
Here is a video that shows you how to zoom in/out
Zoom in/out is located in the top menu bar.
If the time-indicator-bar is not active, the zoom-view will be generated from "left to right" thus zooming in on the beginning of your workout.
If the time-indicator-bar is placed somewhere in the workout, it will zoom in based on that specific location.