Processing Computer Application's Volume and adjusting them?

Hello, I am an absolute beginner in sound programming.

The application I want to make gets all sound processes / process producing sound on a computer - and lets you set a max volume / loudness of each application. I was browsing the JUCE documentation / classlist and there doesn’t seem to be any functions that provide such. Am I mistaken and just bad at reading through documentation?

If so, do you guys recommend any other libraries / tools to accomplish such?

Juce does not have any direct way to process all the sound playing on the system. (You might be able to achieve something with 3rd party virtual audio cable solutions.)