Recording your computer audio

Settings has a Record system audio option. Turned on, whatever is playing on your computer (a video, a browser tab, an app) is recorded along with the screen. That is what you want when demoing a video, a meeting, or an interface alert sound.

In the editor that sound follows the video volume and gets its own lane on the timeline. The microphone stays separate, with independent volume, equalizer and cleanup. On the track waveform, white is the microphone and cyan is computer audio, on the same scale.