If a question has quite a number of responses, it becomes more and more helpful to number each subpart to the question. Of course, doing this manually is not a good idea.
I've managed a workaround by adding
(in GUI form) at the beginning of each of my subparts and then using the following custom CSS:
content: "—(" counter(section,lower-alpha) ")";
It produces a heading that looks like "—(a)—" which you could customise of course. The main thing was using the em-dash in the title itself because I wanted a visual separator in the editor window. This works in a pinch but is a little fiddly and feels like a bit of a hack.
It would be nice to have an editor button that inserted an auto-numbering thing (perhaps could be included as part of the "Block" feature, but maybe just easier as a self-contained object).
I don't know how this would work with adaptive questions :)