With editable: false, the contenteditable attribute on the document node is removed, which by default makes the browser disable keyboard focus for the element. When the node isn’t focused, it doesn’t even receive keyboard events, so it’s hard to implement any keybindings for it.
You could use the attributes prop to add a tabIndex=0 attribute to your editor to make it focusable. But this might lead to some other key bindings also firing, and if those do change the document, editable: false (which works only on the DOM) level won’t stop them.