audio – Can’t control Skype Notifications volume on Windows 10 Pro

I have Skype for Windows 10. There are no options to control the volume for notification sounds either in app or the Volume Mixer on Taskbar. What am I missing? Shouldn’t the Volume Mixer show a volume controller for when a sound is played by the Skype app so that I can turn it down or up?

By the way, I can mute it from Settings, but I just wanna turn down the notification volume.

Thank you very much!