The Swash feature is a place to put the glyphs. You have to check if the feature is available in all apps you intend to use the font. The support for the different stylistic features (ssXX, salt, swsh …) is different in the Adobe App and very partially in Quark.
I’m reviving this question because I’m also in the same boat. I have some swash caps, which i’ve named X.swsh. However I’d also like them to be accessible through stylistic sets. X.swsh.ss02 or X.ss02.swsh does not seem to generate automatic features. (neither ss02 OR swsh). Do I need to do this manually? or duplicate glyphs?