Dual Boot Windows 10 and macOS to External Drive on Macbook

Firstly go through steps: Install Windows 10 to External Drive on Macbook

The following steps will allow you to have one or more macOS installation in a single APFS volume on the external drive.

Install macOS

  1. Boot into Windows and resize Windows partition to make space for macOS installations.
  2. Create new partition in Windows for macOS installations.
  3. Boot into macOS and open Disk Utility.
  4. Format newly created partition to APFS.
  5. Download macOS installation from the macOS App Store.
  6. Once installer starts go through process and select newly created APFS partition for destination disk.

Install Additional macOS versions

  • Additional macOS versions can be installed to the same APFS partition created above.
  • You must first create a new APFS volume within the APFS partition for the new macOS installation.