Default [Q] How to add custom buttons on Navigation bar?

I used to be able to get many more button options for the nav bar on JellyBean ROMs but I seem to be able to add only the menu or search button to the nav bar on KitKat ROMs. Is there any way to add other buttons or would I have to edit the SystemUI.apk manually?

I'm currently running crDroid simple.
If there are any KitKat ROMs which support adding custom buttons, such as the power button, or apps, I would appreciate it if someone could point me in the right direction.