Thanks for the nudge, we do have a Feature Request to make an ‘Outdoor Workouts’ library that should help you when selecting a workout that fits your timeframe, but we’re working on some higher-priority fixes and long-awaited features before this gets on the roadmap.
That being said, since you have routes available to you without a lot of coasting/stopping and you feel as though outside workouts are too long, you should feel free in exercising some autonomy in choosing workouts that have intervals that fit your timeframe and goals, and cutting out extra time beyond the intervals. 