JoyCon Exd can control one onboard LED and two external LEDs.
If you want to control LED with the current preset, check Control in the LED tab. If Control is not
checked, this preset doesn’t control LED and LED keeps previous configuration.
If Reverse is checked, On Off is reversed.
If Turn Off on Sleep is checked, LED is turned off when the PC goes into sleep mode.
LED control has 8 modes.

0. Always On : LED is turned on always
1. Always Off : LED is turned off always
2. On by a button : LED is turned on while a button is pressed.
3. Blink by a button : LED blinks periodically while a button is pressed.
4. Toggle by a button : LED is turned on by pressing a button, and is turned off by another pressing the button.
5. Toggle blink by a button : LED blinks periodically by pressing a button, and is turned off by another pressing a button.
6. On by a button, off after a period : LED is turned on by pressing a button, and is turned off after a period automatically.
7. On by any button, off after a period : LED is turned on by pressing any button, and is turned off after a period automatically.
Unit of Period is millisecond. In the blink mode(3, 5), turning on is one period and turning off is another period. For example, if the Period is 500(ms), LED is turned on every 1 second(1000ms).

To assign a button to LED, drag-drop a button to a LED.