Do you mean permanently?

Here is an excerpt from the manual.

Additional UI settings are available to control the button back-light. While in the battery check mode (accessible with 3 fast clicks), press&hold the button. A double flash followed by a single blink is again the prompt for the first setting:

1. Button LED on while GTmini OFF

1: Disable 2: Enable [default]


2. Battery level blinks on button LED only

1: Disable [default] 2: Enable


3. Button LED

1: Disable 2: Enable [default]

So what you want to do is 3 fast clicks, it will blink the battery voltage, then press/hold the button. It will do 2 fast, 1 slow blink. Then 2 fast, 2 slow blinks. Then 2 fast, 3 slow blinks. Here you have maybe 2 seconds to click the button once. The main beam should blink when you do it. Then just let it finish. I’m not sure what it will do. Maybe 4 fast blinks. Anyway, once it’s not doing anything, try turning the light on and see if the button light is now off.