Hi
The Workout app on Apple Watch does not currently specifically support run/walk workouts.
If you would like to submit a feature request to Apple, then you can do so here:
Feedback - Apple Watch - Apple
When recording specific fitness activities, be sure to use the Workout app (or a third-party app that shares data to Health) and to choose the activity type that most closely matches your workout, including choosing Other for any workouts that are neither included within nor sufficiently similar to those in the main list. This enables your watch to use the most appropriate sensors and data sources when tracking results:
However, note that neither distance nor a route map are recorded for Other workouts.
For interval training workouts, you may find that a third-party app meets your needs. Apps that you may wish to consider include, for example:
Intervals - Interval Timer on the App Store
Be sure to check the app description and developer's support resources to check whether any given app meets your needs.