If node-ftp doesn’t suport it, I’m afraid I wont add it :(. Have you tried to play with configuration file? The configuration get sent as-is to node-ftp connect method as describe here
secure - mixed - Set to true for both control and data connection encryption, 'control' for control connection encryption only, or 'implicit' for implicitly encrypted control connection (this mode is deprecated in modern times, but usually uses port 990) Default: false
secureOptions - object - Additional options to be passed to tls.connect(). Default: (none)
For more information on secureOptions, it’s here.
I’m sorry for the lack of documentation, the package is still in development