How use function keys in iPad with Apple keyboard?
When using the Apple Wireless Keyboard with an iPad device, not all function keys work. From Apple's Support Article:  Apple Wireless Keyboard and Magic Keyboard compatibility with iOS devices:



Since the Fn keys don't work per Apple, it's a safe bet that you won't be able to remap them.  You have to recognize them in order to reassign their function.

This is most likely the reason that you will need to utilize the softkeys provided for by the App.



What you can try is using the Escape sequence: Esc #  combination where # is the number of the Fn key you are trying to press (i.e. Esc2 for F2)