First, we'll need to get a GUID:
PS> [guid]::NewGuid()
Guid
----
75910903-ae85-44bb-95d9-f200eea9a8a9
Then, open Terminal settings and add a profile:
{
"guid":"{75910903-ae85-44bb-95d9-f200eea9a8a9}",
"name": "Node.js command prompt",
"startingDirectory":"C:\\Program Files\\nodejs",
"commandline": "cmd.exe /k \"C:\\Program Files\\nodejs\\nodevars.bat\"",
"hidden": false
},
(All of those extra backslashes are to escape characters that would mess up our JSON strings!)