Updating a published world with a duplicate version : what's the smooth and easy way?

Hi everyone, I would like to know how to update my published world with another duplicate world I worked on during the last week? Let's say I have the world published for the competition, I duplicated it and worked on the duplicate file of the world to improve it. Now, if I want to update my published version, I noticed there is no way to select the new duplicate version and upload it on the published world. If I select Publish on my duplicated world and continue to go ahead it will publish a new world and not updating my published frist version. What's the right way to do that? Thanks in advance.