Can an external switch be connected to the DISC PENDANT 100-230V?

Yes, it can. But this may not be an LED dimmer.

Important: If you want to use an external switch, keep in mind that when the switch is in the OFF position, the light cannot be operated by the sensor. Also, the light will be subjected to an automatic calibration process the first 15 seconds each time the external switch is switched from the OFF to the ON position. During this time, do not place a hand or conductive objects near the sensor because this will interfere with calibration.