I wasn't able to : (
By disabling character swap the game also disables the Defeat screen. I haven't found a way to bring it back nor restart the game after death. I'm not sure how to then on top of that restart from the last checkpoint since I haven't found great resources online for how to use the editor.

Tell me, is it possible to make it so that when you turn on the hard mode, after death the game restarts the level (updates enemies), but the spawn would be at the last checkpoint?