I have a Glyphs file with the source for uprights and italics. It has a single-storey a, which is implemented as a.ss01 (plus a with diacritics).
In the italic instances I activate this via CP Rename Glyphs *.ss01=*. This means that in the Italics, ss01 activates the double-story a. Elegant! Well, but rather impractical. Assume the user has a chunk of text with a mix of uprights and italics, and they want to activate the single-story version throughout. You can’t simply apply ss01 to the whole text. It is much better to provide different stylistic sets.
This is why for the italics, I simply want to “rename” the feature ss01 to ss02. Is this possible via custom parameter? Using Remove Features and Add Feature is a bit unelegant and doesn’t auto-update (which, as you may know, is really unbearable for me). Plus, it seems I can’t give it a description, and it will be in the wrong order.
In the source file, I have ss01 as well as ss02. ss02 contains the auto-generated text from ss01 via manual copy & paste. In the upright instances, I use Remove Features ss02, and in the italic instances I use Remove Features ss01. Both features can have the correct description, of course. Voilà! (The only remaining problem is that ss02 does not auto-update when I change the glyph set.)
This is also why I would really like to see a feature which allows me to define custom suffixes which should be used to generate feature code. In your example, I would like to define “ss01” as a suffix which should be picked up to generate ss02.
I occasionally get projects where glyphs are named alt1, alt2, etc., and used across multiple stylistic sets. Automatic feature code generation would be easily possible if I could simply define a list of suffixes that Glyphs should use for each stylistic set.
