And remember that "Voice", "Music", and "Sound Effects" tracks are all audio tracks. You can assign any name you want to a track. See online Help (F1) for Tracks > Video or Audio Track Controls, also Inserting.

Shouldn't the audio track of the video appear below the video track automatically

Yes.
See the posts by musicvid and Warper in this thread. You might possibly find something there.

I think OP is right, in that mostly the audio is under the Video - but it depends where you put the video.

If there isn't an audio track position near, then it will appear some way below.

-OR- is OP saying the audio is missing altogether?

I suggest he tries to enlarge the tracks (Screen RH controls). This makes the audio easier to see (and edit, etc)...but you have to scroll up/down as the Video may be some distance from the audio. In my experience, as the Project gets more complicated the audio can appear to be further away. However, as already posted by ANOther, you can name the tracks, so if the vid track is named "waterfall" then you can name the audio similarly. I'm not saying this is a good Method, rather as an example.

I'm not aware of the reason Audio cannot be right next to video (or text which I sometimes animate with Keyframing, so a SFX is needed).
+ I suspect this is a Legacy issue, when there were relatively few tracks available - it didn't matter.
A simple fix would be to colour-code the tracks (using the Electrical colours, Brown=1, Red=2, orange=3, etc. this is International). I know you can add colour, but it will be User-choice, whereas a default "Electrical-Track-Colors" would sort out the first ten. The Colour need only be a Frame round the content, I'm not suggesting the track is coloured as this would make Editing difficult.
....No doubt other Users can suggest better....