It would be useful to have a magic word (or some mechanism) to override the default category sorting behavior. For example, I'm assigning alphanumeric sortkeys in a Lua module, and would like to use 0,1,2,3,4,5,6,7,8,9 separately. Categorized pages using sortkeys of A, B, C, etc. all show up under their respective headings (A, B, C, etc.), but 0, 1, 2, etc. are all grouped under "0-9".
Danny Horn was involved with changing the category sorting algorithm 2 years ago so I've subscribed him. Original talk page discussion here.