cant use them
They’re not buttons. They’re indicators to let you know that Nvidia Shadowplay is running. The first one is the mic indicator and the second one is the video recording indicator. They have nothing to do with MSFS2020.
When ShadowPlay is recording, you will see a green icon.
That circular icon is “Instant Replay”. Activated with Alt+Shift+F10, it sits and records footage, of anywhere from 0.25 to 20. Think of it like the Sky active pause. At any time, you can hit the Alt+F10 key, and it will save the currently recorded footage as a file. Kind of like a continuously rolling cache you can opt to save out at any time.
Useful if you see something interesting, and want to keep it. I’m not sure where the rolling cache version of it sits though, but Alt+F10 will save the file in the same location as regular ShadowPlay will.