Ultimate Edition with latest patch.

So, I'm posting here as while this is an issue with a Win10 component, WOFF is the only application/game that has this issue.

The issue is that when CMFS3 itself is open, the volume mixer is inoperable. This means it's impossible for me to balance it's volume, specifically engine sounds (which even at WOFFs lowest setting is far too loud) with VOIP applications or background audio/music.

Anyone have this issue and a solution, or is this just the price of using old software on a modern machine.

I can not follow you, what are you trying to tell?
If you are starting the flight, thats is the point CFS3.exe comes in, you can not adjust the windows volume, while playing music on the background and talking over the internet phone? Or did I read this wrong?
Could you please explaine us more on this.

edit: a print from your screen maybe?