Amber Audio
This is the Day
Look for a Dell Utility like this for your model number it might give you more options, think it was mainly to fix Win 8 thoughNope, enabled it in BIOS. Annoyed it times out and there is no option to keep it on all the time.
https://www.dell.com/support/home/en-uk/drivers/DriversDetails?driverId=MHVWP
These are the common commands depending on the Dell model to control the keyboard backlight. Repeatedly pressing the combo cycles through on/off/dim/bright. Newer ones a ALS - ambient light sensor. The light goes off to save battery if no keys are pressed for a few seconds.
Dell E6440 is FN+Right Arrow
A couple others are ALT+F10 and FN+F10 and F5