When you save a complete workout, you will have to name the segments within the workout. A workout will always have at least 1 segment and a cooldown. A segment in a workout could be "a warm-up", "a climb" or something similar. You can split your workout into as many segments as you like.
Here is a video that will show you how to split a workout into segments
The interval marked as "split into segment" will be an Active Recovery-period in your workout. Here is an example of a workout with 3 segments. The arrow in the top indicates what button you need to click to input split into segments. Don't forget to add a cooldown to save the workout.
If you forget to add "split into segments" in your workout, you can always add them later by marking the interval BEFORE the place you want to add a new segment, and then click to add it