Yes, I ran into the same problem, and Apple-ism seems to be a good term for this issue 🙂
It works this way:
- Select (or highlight) the code your want to turn into a snippet
- EDIT: Click and hold (do not drag!) on any part of the selected text for a short moment (like 2 seconds, sometimes 8 seconds)
- EDIT: The mouse cursor will change icon (not on El Capitan).
- Now you can drag the code over the snippets library, where a green + icon will appear. EDIT: On El Capitan the green icon does not appear, but the frame of the code snippets window will become thinner.