No, good questions, because it's not covered in the manual (at least not in any detail); the system uses Unicode character classes, for the most part. You can, however, use the RESERVE keyword to force the system to recognize digraphs as a single symbol, or you can use tie-bar characters t͡s.

You would have to do the latter; I sort of designed the SCA to force you to do that, since I think it makes the mechanics of the sound change more explicit and naturalistic. Maybe others would disagree.

Also, this might be a good time to mention that I basically completed the scripting functionality but haven't made a release of it yet. Mostly, I need to update the manual.