The Function Keys (FN) I am referring to are located at the top row of your notebook consisting of F1-F12. Why the need to make it permanent? If you have used MacBook, you will appreciate the convenient of having the useful functions such as Wireless On/Off, Volume Up, Volume Down, Mute etc (which are designated with blue icons which must be used with the Fn key) just by pressing the Function keys directly instead of Fn+F3 for example.
Now the bad news, not many Windows-based notebook brands support this feature. My Toshiba Ultrabook supports it and it was deal breaker that I purchased Toshiba.
Here is the procedure to enable it for the Toshiba notebook:
Step 1: Look for the Toshiba system tool using the Search Tool, see picture (Click to enlarge)
Step 2: Navigate to the Keyboard tab and select “Special function mode”
Step 3: Need to reboot to take effect. It will after boot completed!
Turn on and off keyboard backlight
Keyboard backlight can be enabled and disabled using the combination Fn + Z (or Y depending on the keyboard layout).
There should be a tiny keyboard icon on the button (see picture).
Other useful links: