hi everyone can anybody know what's this botton for ? It a vellfire 2013.

Aftermarket. 

Could be anything. 

Do you have any additional driving lamps, lighting inside?

Dashcam or cameras in general? 

Usb posts somewhere?

There are two ways of finding what it is.

 

1. Press it and look around at everything to see if anything changes. 

 

2. Pull the switch out and try and follow the cable.

 

On some cars people have put a switch into the brake signal wire so they can watch TV while driving

 

Could it be dash panel illumination intensity ?

Throttler / remapper?

Passenger Ejector seat... never know with the Japanese aftermarket gadgets, certainly a 'power symbol' maybe it has been disconnected I have a similar but smaller button which was for ETC (electronic toll collection) device.

 thanks mate😊👍