Changing hero shortcuts

I looked all over and couldn't find the answer to this. I need to know how to alter the customkeys.txt file to change the shortcut for the fifth hero from f5 to another, like f12. I know that i can do an autohotkey script to type f5 when i do f12, but f5 turns on a program already, and will not select the hero.

I have the Customkeys from the Dota Customkey Generator to change the keys for voker, that i want to update with this.