This made me interested (I still haven't imported my rather massive bookmark file to the 770) and I did some quick checking. The bookmarks seem to be stored in /home/user/.bookmarks in an XML file. Presumably, this is in XBEL format - if so, it should be possible to copy the file off the 770 and work on it with any XBEL capable software to sort etc and then copy it back.

Haven't tried it yet, but I probably will. We'll see how it goes.

I don't know any way to sort on the 770, but I haven't really tried either so I may just be uninformed...