Reply to my own post - I was able to set the configuration by using the Configure tile I added to the device type.
It seems that even in USB powered mode, you still have to set the sensor into a state where the LED is blinking before it will accept a configuration command.
After much trying (and not knowing what the final combination of press/hold the button on the sensor turned out to be), my sensor is updated. It’s now reporting No Motion after 60 seconds.
I may update that again to 15 seconds, since I’m not worried about power usage.