Have you had a look at the Launchpad thread in the developer forum?
https://www.mobileread.com/forums/showthread.php?t=97636
You can use it to assign different functions to "hotkeys" on the Kindle. I know you can simulate page turn keystrokes with it, so I assume you could assign the five-way functions to other keys, but I don't know for sure... I don't use the hack myself, but check out the thread. If you have any questions, I'm sure someone who uses Launchpad will be able to answer them.