The Final Standing
Tournaments all have a 'Final Standing' feature that lets organizers declare how participants fared during the competition, and what rank they reached. It is available via the menu item.
Once here, you can add new entries in the Standing by clicking the '+ADD' button in the top-right corner, then enter a Rank, and select the participant for that rank in the list. You can start typing a participant's name if you have a lot of them.
You can create a standing that goes from one to your total number of participants in the tournament. They can be tied (as seen for the 4th rank in the screenshot underneath), but in that case, the next rank has to be increased accordingly (a tie between two participants for 4th place will prevent a 5th place from being attributed), depending on the number of tied participants there are for this rank.
This new feature comes with its public page that is available for all to see, via a new "Final Standing" item in the tournament navigation. There also is a new Standing API Endpoint for developers to retrieve the Standings information, for display or use in more advanced rankings such as seasonal leaderboards spanning across several tournaments!