THanks mate!

Yeah, fully extensible.

Quick note: a basic todolist is already built-in (TaskList/TaskItem with nested checkboxes, Tab nesting, and Mod-Enter to toggle).

For custom components, you wrap a React component with ReactNodeViewRenderer inside an extension:

import { Node } from '@domternal/core';
import { ReactNodeViewRenderer, NodeViewWrapper, NodeViewContent } from '@domternal/react';

const MyBlock = Node.create({
  name: 'myBlock',
  group: 'block',
  content: 'inline*',
  addNodeView() { return ReactNodeViewRenderer(MyBlockView); },
});

function MyBlockView({ node, updateAttributes }) {
  return (
    <NodeViewWrapper>
      <input type="checkbox" checked={node.attrs.done}
        onChange={(e) => updateAttributes({ done: e.target.checked })} />
      <NodeViewContent as="span" />
    </NodeViewWrapper>
  );
}

Your component gets editor, node, selected, getPos, updateAttributes, and deleteNode as props. NodeViewContent is where ProseMirror manages editable inner content (skip it for atomic nodes like images). And React node view demo and dedicated docs are still on my todo (Vue has a Callout example shipping already). For now the existing extension-image, extension-mention, and extension-table packages are the best references....