command+alt+down: with selected text, extract text to new block. At the end of a block, create new empty block below current block.
command+alt+up: at the start of a block, create new empty block below current block.
alt+shift+n: new chapter
esc: toggle UI
Other useful shortcuts
Clicking on an item in history will restore that editor state, wiping your current editor state. But if you command+click on it, it will restore that state into the current block only. So your current block will be cleared but everything else will be left untouched.