It is not possible. When you publish a video to YouTube that is considered a finished product, just like a news article. And like a news article you are not able to go back in and make edits to that in order to change the narrative. Once you publish a video that is it; you need to make sure that everything is completely finished and ready to go when you begin to upload because there is no going back!
The only catch to this is the YouTube editor but be advised; the purpose of that editor is to either trim the ends of a video or delete/mute/blur a segment. This editor is not for actually editing the content, rather it is intended to give you a tool to help should you run across minor copyright infractions that can be solved with these very simplistic edit features.