I plan to have an option for the Dungeon Master to label such Characters as "Dead" so they go into an "Archive" mode. They will not be totally deleted so it is kept as an archive of previously created Characters.
I could see this especially helpful if a character that has died is later resurrected or brought back to life.
What about players that create multiple characters and only meant to create one, is there a way they can undo the extras?
No reversal to it. They can use the character at some future point. I am supposed to code in something to give the GM power to regulate how multiple Characters are used. For instance, marking them as "Dead", "Resurrected", "Away" and so on.