The answer from WD support for me was:

"Thank you for contacting Western Digital Customer Service and Support. My name is Bill.
I understand that you would like to know more about the power switch on your WD Elements desktop device.

This power switch is designed to be used exclusively with WD Smartware Pro software for Windows.

However, this software is no longer available and is no longer distributed or supported. You can turn off the drive by unplugging the power cord after safely ejecting the drive from your computer."

This means that without the software mentioned above, you should no longer press the button on the back of "Elements".

PS: With Windows 10, since version 1809, it is no longer necessary to safely remove USB hard drives with "Eject". Since then, if you are no longer accessing the hard drive, you can simply unplug it.
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