On my Thinkpad X220 there's a blue Thinkvantage button that only gets used when the machine boots to select different options.
Using xev the button is referenced as XF86XK_Launch1, here I use it to run a rofi menu for logging out, shutting down, rebooting, etc.
dwm/config.h
...
{ 0, XF86XK_Launch1, spawn, SHCMD("rofi -show power-menu -modi power-menu:rofi-power-menu") },
...
power-menu can be found here
ยง