How to Use 7.1 channel outputs independently?

I have a MSI B450A-PRO Motherboard. It has a 7.1 channel audio output. I want to use a some channels independent of each other, like I can use the Front Headphone OUT, Rear Speaker out, and other digital outputs connected to the system.

So, I can get some more switchable audio outputs.

right now I have a 5.1 system hooked up to the output, and the SS (Side Speaker) output is unused. I would like to use this SS out for another speaker, with a different application and audio source. Is this possible ?