When clicking on "Add link" in the "Social Links" Dashboard page there is a dropdown with possible social link entries like Facebook, Twitter, Instagram and so on. Here I'll show how to add other links with the example of StackExchange.
This How-To is for adding fonts to the Redactor plugin "fontfamily" in a package. The original fontfamily plugin just adds a dropdown with a few fonts.
Change the default " :: " separator to something else.