Voice volume meter

My son with autism has difficulty knowing how loud he's talking, especially when he's excitedly playing video games with his friends over Discord. This is hard for his friends and hard for those of us in the house with him. Visual volume feedback is a very effective tool to help him, but I've had limited success setting up a third party app for this that will work alongside Discord and the variety of games he plays. My hope is that something could be built into the Discord client itself (on Windows) that would show a simple volume meter as he's speaking. The catch is that it would have to be able to show over a full screen game, which is where third party apps struggle most. I know this isn't a feature most people would use, but it would be invaluable for those with autism as voice volume moderation is a common struggle.