How to create a hardware shortcuts in Android 4.3? I have Samsung Galaxy S4 GT-i9500 running the latest firmware with Android 4.3.

I want to create "hardware shortcuts".

For example, if I hold volume up and home at the same time, then it'll open an application that I set, for example "Firefox".

As a Linux user, I know it's possible in Fedora and Ubuntu.

Is it possible with Android? My device has not been rooted.
From the description, it seems like Button Savior Non Root can do this (and Button Savior (Root) even more). I didn't try it, and the description is slightly unclear whether it only emulates hardware keys using a floating menu, or you can re-map hardware keys; so your feedback is welcome if you try it.

Alternatively, the XDA developers offer an app called ButtonRemapper. While this explicitly states Tool to remap the hardware buttons, it requires root.

Last partly alternative I can name is tasker. Here I know for sure you can remap at least the camera button. Not sure about others.