Few more things I forgot to mention:
The [Add an Obstacle] dialogue is somewhat confusing, with offering to “Add some obstacles”. I suspect this would be “Add ObstacleChallenge Elements”?
I’d further suggest adding one Element (with a single checkbox) automatically, if none are defined - empty Challenges are rare, and this might save a lot of clicks.
More click-saving: Whenever adding a new Element, you might want to automatically call the [Edit] function, and focus the description input field.