After exporting your video to YouTube, the video conversion button will change into a 'Watch on YouTube' link which you click that redirects you to your video.
Sometimes, you want to make an edit to the video! To do so, simply open up your video and make the changes you wish. Once you click save, the 'Watch on YouTube' will revert back to the quality
Once you render it again, a new YouTube video will pop up in your account with the changes you've made!
Please note that this will not overwrite the previous video on YouTube, but will export a new version of the video.