I want to complete the assets importation automatically, not by dragging files to the editor manually.
Is there a method to import .wav files from one directory to the UE4 editor as assets automatically?
Yes if you put your stuff in /Content of the game it will automatically be seen by the editor, and you can say “yes” to import (it will prompt) once.
Also read this doc. Reimporting Assets Automatically in Unreal Engine | Unreal Engine 5.2 Documentation