How do I disable Wi-Fi roaming? (disable autoconnecting to the strongest AP) I can't find a way to disable Wi-Fi roaming on my Mac so I can connect to a specific AP and stay associated to it without roaming to the strongest AP. Is there any way I can do that?

My MacOS version is High Sierra 10.13.2.

I have already tried all airport JoinMode settings ( /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport prefs JoinMode) and the "airport-bssid" tool that is available on GitHub, and both solutions didn't work.
It is sort of possible to do but the wording is not clear.

If you open System Preferences > Network and click on the WiFi icon on the left side of the Network Preferences window you will see two checkboxes below the Network Name pop-up menu. On my Mac it looks like this.



For your situation I would select your preferred network from the Network Name pop-up menu, and check both checkboxes so that it will auto-join your preferred network and force your Mac to ask to join other ones.

That is the only way I know to even get close to the settings you need without 3rd party software.