The button Audio from the render tab is taking valuable space. Generally to render out an audio (file.flac) we would expect it from the video editor since it´s a "mix" down.
"Layered" audio is only viable through the video editor workspace.
On another related matter, there should be an Audio button (not the same from above not its functions) in the timeline, since this is how normally an animator "plays" the audio (scrubbing) to synch the animation. That audio button would load the audio file in the video editor workspace (like normally is, now).
Finally, to add "sound" to the final animation render, on the render properties>output>FFmpeg video and >Encoding>Presets the options already show that SOUND will be included. So there´s no need to create the extra button on the property panel next to the render/animation buttons.