How to set default value of ipv6.addr-gen-mode with eui64

Issue

• How to set default value of ipv6.addr-gen-mode with eui64

# nmcli con show <CONNECTION-NAME> | grep ipv6.addr-gen-mode
ipv6.addr-gen-mode:                     default

man 5 NetworkManager.conf:

ipv6.addr-gen-mode
  If the per-profile setting is either "default" or "default-or-eui64", the global default is used. If the default is unspecified, the fallback value is either "stable-privacy" or "eui64", depending on whether the per-profile setting is "default" or "default-or-eui64, respectively.