How can I configure my virus scanner to automatically scan files downloaded with IDM?
Please note that for antiviruses that have some kind of realtime protection it is not nesesary to add any settings in IDM. They will scan all downloaded files automatically.
Please try to find in Internet on sites of antiviruses special test file iecar.zip - imitation of a virus and download it with IDM. And you will see that on the fly protection will work without setting virus scanner settings in IDM.
But on the other hand such antiviruses try to control all hard drive activity and all network traffic that in some cases may damage IDM temporary files and lead to corrupted downloads.