Controlling master volume through Blueprint / C++

Is there any way to control master volume for the entire game through Blueprint?

It seems like you can control the volume for individual sound effects etc. but I can’t find any way to control the volume for the entire game…

I understand it might be necessary to write some C++ to make a node for this. I’ve spent the last couple of hours trying to figure out how, but can’t get anything to work as my C++ knowledge is atrocious.

Any help much appreciated!