I think is still unresolved on this issue. If I enter the "last name" of an author as al-Kindi, it still is sorted under 'A' (and not under 'K', as it should be). On the other hand, as I include al- as the last part of the "first name", it is space-…
I think this patch has not yet been included in standard Zotero distribution. I'm currently using Zotero standalone 4.0.27 and the MS-Word plugin, but a surname such as al-Kindi is still sorted in bibliography under 'A', not 'K'.