This macro will check every 5 seconds for the name of your default audio input device and your default audio output device, and display each of those names on your system menu.
Audio Source Detect and Display Macro (v11.0.3)
Audio Source Detect and Display.kmmacros (6.2 KB)
Now that I've uploaded it, I see a very similar solution posted on this page. It uses the same underlying mechanism but has a different approach to the extraction of the name.