apparently in 2014 NM team introduced such a feature -- to specify priorities for different networks. There is now connection.autoconnect-priority.
https://www.hogarthuk.com/?q=node/8 provides lots of information on how to interface NetworkManager via nmcli. E.g. with
nmcli -f NAME,UUID,AUTOCONNECT,AUTOCONNECT-PRIORITY c
you can list known networks and see their default priority to be 0. Now I have ran
nmcli connection modify HOME-WIFI connection.autoconnect-priority 10
to give my home WiFi higher priority (I have the same work wifi points available at home as well, but need to connect to HOME-WIFI when I am home). That command heavily rewritten /etc/NetworkManager/system-connections/HOME-WIFI which added autoconnect-priority=10 into [connection] section -- time will show if it works as it should ;)