Resolved: Creating a File that Imports & Immediately Exports Components Again

// file 1
import Box from '@/components/Box'
import Popup from '@/components/Popup'

const MDXComponents = {
  Box,
  Popup
}

// using MDXComponents somewhere in file 1

// file 2
import Box from '@/components/Box'
import Popup from '@/components/Popup'

export default {
  Box,
  Popup
}

// file 1
import * as MDXComponents from './file2'

// using MDXComponents somewhere in file 1

export default {
  Box,
  Popup
};

import MDXComponents from './file2';
// And then destructure the object like any normal object.
// You can't do import {} in this case, you get the full object.
const { Box } = MDXComponents;

export {
  Box,
  Popup
};

// import all named exports
import * as MDXComponents from './file2';
// or just one individually
import { Box } from './file2';

export { default as Box } from '@/components/Box';
export { default as Popup } from '@/components/Popup';

// If a module has named exports (not just a default export) 
// and you want to export them all:
export * from 'some-module';

// Or just some:
export { someOtherThing } from '@/components/Box';
export { default as Popup, someOtherThing } from '@/components/Popup';