It might be possible to do that in Intervals.icu but that isn’t supported by Suunto or Garmin so you wouldn’t be able to push them to your watch. You could create long enough steps and include the up/down in the text and use “press lap” to end the step when done.
Thanks for your answer, very clear!
That’s what I am doing currently, but not very handy to constantly look at the watch to see elevation.
Hope it will be possible one day.