It got, err, suggested to me that I make this a Product Suggestion.
There is no option to put “Order of Appearance” as a sort field in a custom bibliography (yet it does exist as a stand alone field). This means that an author with multiple same-year citations can end up having their first in-text refence listed as “Smith, 2007c” when the reader hasn’t even seen Smith “a” or “b” citations yet.
This is quite troublesome when you must have an alphabetical bibliography, but need multiple citations dealt with in order of appearnace and not in the (apparently) default order of “Title of Document”.
A fudge to deal with it was hashed out on the forums (and thanks, btw, for having these forums going) but it would be most welcome to add this to the already bewildering array of biblographic sort options.
The link to the previous discussion should be here.