If you click on the "Challenges" tab in the top of web-based Strava you get a nice overview of all the available changes and it shows which ones you joined. Unfortunately, as far as I can see, on this page it is not visible on this page:
- Which challenges you already completed
- What the progress is on your challenges, e.g. 8km out of 100km target
Adding this helps in targeting a specific challenge to complete and prevents that you have to click through on each challenge to see its details.