How to safely eject external

[bjm_]

Go into Task Manager and end task on Hasleo.
It really doesn't matter though since windows doesn't use delayed write on external drives.
You can safely just unplug it.

Oh okay...interesting.  I was not aware "Quick removal (default for external drives)". 
I'd still like to understand why device is (remains) currently in use. 

• Quick removal (default for external drives): This setting disables most write caching to the drive. Data is written directly to the external drive as soon as possible. This ensures data integrity and allows the device to be unplugged safely without needing the "Safely Remove Hardware" notification, provided no file transfers are actively in progress.