Q: macOS: Disable promiscuous Wi-Fi scan and/or display of unwanted list of Wi-Fi networks? I am annoyed by a display of all nearby Wi-Fi networks around me, when I know I am looking to connect to one among the couple of known networks.
Is there a setting to disable detection of new/unknown networks? I looked at System Preferences app → Network → Wi-Fi → Advanced, but could not find anything relevant to this requirement. It is more of a matter of reducing clutter than any major hindrance.

A: 
Is there a setting to disable detection of new/unknown networks?

No.
Entering password to connect to known access points is a one time activity. May I ask, apart from aesthetics, what's your rationale for suppressing the display of the list of discovered networks?
There is no built-in setting to suppress the display of list of discovered, non-hidden Wi-Fi access points in iOS. But ever if it were there, it will only make things hard when you'll wish to connect to a new network (which, varying from person to person can still be a common use case). You'll have to manually enter the SSID and password for the access point.
Also, if it were possible, you won't be able to benefit from the Wi-Fi password sharing feature available since iOS 11 and macOS High Sierra, which lets you quickly join Wi-Fi networks your contacts present nearby are already connected to.
