Carefully using a thin screwdriver to remove the top panel of the switch, and then you will see a small light bulb, this is the indicator that glows when the light is off. First, I can turn off the meter to avoid electrocution.
The indicator is attached to two terminals. Disconnect one of them, after which the indicator lamp will not burn. You can completely remove the led. If not to damage the bulb, then if necessary it can be put back pripal soldering iron. In any case, the functionality of the switch is not affected.
Put back the removed panel switch, should be a "click" which will mean that the panel is securely fastened.
If you mind the light, but removing the led from the switch you don't want to, then just seal it with a piece of masking tape, then light emitted by the led will dim and cease to interfere with sleep at night.