I see the method to add variable and it allows you to spec attributes and file extensions...but I want to be able to add attributes and file extensions to existing variables from an add-in or stand alone app.  The API documentation that I have leads me to believe that this isn't exposed.  There is an EditVariable call that opens the variable dialog...but that seems as close as it gets.

I also looked at the DB tables...that looks pretty straight forward but I was hoping there would be an avenue given by the api.