Both
Volume² v1.1.6, build 413 (07.19.2019) download:
and
Last Release version V1.1.5 Volume², buil d 404 (12.31.2017)
do not show any icon or interface after installed.
Download Volume2...

Yes, that is probably what I want. Thanks for sharing.
I will have it tested tomorrow.

Let us know how to do that or get any download. Best if I can show the volume bar of specified app as I have multiple sound apps running. eg. game and youtube.
I am now checking
"How to customize...

I have multiple audio devices so I want app or programs to send sound to different devices.
for example, I want sound from game program send to my bluetooth speaker/handset but the youtube playing...

I want to display the volume control topMost so I can see the volume bar moving up and down . Is there a way or any app/download can do that?