We are creating a font with alternatives for each letter (3 versions). We have pasted Adobe Illustrator artwork into the Glyphs program but have not been successful at getting the alternates to activate within the exported family. They all show up in the Mac Repertoire menu in Font Book but are not able to be accessed. We have only been able to activate one font. We have used many different suffixes on the alternates (.alt, .001, ss01, etc) with no success. Is this even possible to do within this program?
The Apple text engine only supports a few OT features. ss01 should work though. Do not forget to update and compile your features in the Font Info.
And you probably have a font cache conflict. Read this:
http://www.glyphsapp.com/tutorials/eliminating-font-cache-problems
Did you have any feature in Font Info > Features? If not you need to generate them or write them yourself.