Selectors and associated fonts from an existing project's stylesheet can be imported into another project's stylesheet. This allows the user to clone some or all of one project without having to key in complex selector names or find the correct fonts. It takes three API calls, but it does make life easier for the user.
Think of the first project's stylesheet like a menu. The menu is created by exporting a stylesheet from that project, and the menu is read by importing it into another project. Then the selectors (and their associated fonts) are "ordered off the menu" by using the Add Stylesheet API call.