Cannot keep modifiers pressed with USB Device Key Trigger

I would like to use a USB Device Key to keep modifiers pressed: Shift, Option, Ctrl, Cmd.
I've tried this method, but it does not seem to work for modifiers:¨

I've tried both "Pressed" and "is down", but both fail to trigger the corresponding modifier.

Keyboard Maestro 9.0.5, OS X 10.15.5

X-keys Macros.kmmacros (4.5 KB)

You cannot use Keyboard Maestro to generate modifier keys like that.

Keyboard Maestro can keep a simulated modifier pressed, but only while the macro remains running, and it only applies to simulated events - real events will come with their own real modifiers.

So you cannot use Keyboard Maestro to act as a modifier.