I think it's in the redesign. So it might be available when the new BGG goes live.
The redesign is on hold.
However, this suggestion is certainly already on the radar as one that will be implemented:
Sort Order in GeekLists: (status: will be implemented - see here)
Decending Order Geeklists (by CheetohFingers)
Geeklist Sorting Ideas (by basilmichael)
Override default sort order for a geeklist (by Martinus)
14/09 14-07-11 Geeklists - allow users to change sort method (by tesuji)
geeklist sorting (by ddyer)
09/08 17-08-11 Suggestion: GeekList Ultra-'Collapse' (by Necromancyr)
04/05 05-11-11 An option to SORT Geeklist by THUMBS would be awesome (by kevintlee)
02/04 23-04-12 Geeklist adaptability for each viewer (by Redward)
03/06 30-07-12 Geeklist sort! (by cabol)
11/14 29-06-12 Sorting geekslists (by calandale)
01/03 25-08-12 tools to reorder geeklist (by ddyer) (status: will be implemented)