Updating the answer as it is now possible to reset the leaderboard during development.
> You can only reset player progress data for your draft leaderboards.
>
> To reset leaderboards in the Google Play Developer Console, click the
> button labeled Reset leaderboard progress at the bottom of the form
> for that event. To reset leaderboard data programmatically, call the
> Management API Scores methods.
Reference: `https://developers.google.com/games/services/common/concepts/leaderboards#resetting_a_leaderboard`
Present in both answers;
Present only in the new answer;
Present only in the old answer;
