I can concur with phi.lho, and I would follow the practice of having the enums as a separate class/file, and that extends to using enums in a library (otherwise you will have problems accessing the enum in the processing sketch). The ide will complain if for example you try to import an enum nested in another class (eg povwriter.Options.Quality where Quality is the enum), note if you don't explicitly import in that way the enum cannot be accessed. However if in my example you have povwriter.Quality (a separate enum class/file) then Quality enum is accessible with a package import.