How to partition USB drive in Windows 11/10
Use MakeWinPEMedia to create multiple partitions on a USB
To be able to work with USB drives that have multiple partitions, your PC has to be Windows 10, v1703, with the most recent version of the Windows ADK installed. Windows Assessment and Deployment Kit offers tools to help you customize Windows images for large-scale deployment and to test the quality & performance of the system. MakeWinPEMedia can format your drive as FAT32 which has a file size limit of 4GB. Since you can create a USB drive with both FAT32 and NTFS partitions, you can use a single physical drive to boot to Windows PE as well as store large custom images. The following creates two partitions on a USB drive; one 2GB FAT32 partition, and one NTFS partition that uses the rest of the available space on the drive: For more information on how to create a Windows PE (WinPE) bootable USB flash drive or an external USB hard drive visit MSDN here.
Create multiple partitions on external drive with Disk Management
Windows 10 with ADK installed allows you to partition USB drives too, using the Disk Management Tool. To do this, connect your USB or external drive and from the WinX Menu, open Disk Management, and follow the same process as you would for partitioning any disk.
Use Bootice to create multiple partitions on a USB
Incidentally, you can also use freeware like Bootice to create using Parts Manage > Re-Partitioning > USB-HDD mode (Multi-Partitions option under the Physical disk tab). Hope this helps!