Author sort is normally just the sort version of the Authors field.
2 names = 2 sort names (and these are really 2 name entries in the Authors Table)
The DB stores an Author Index record for each one separated by the &
& is a separator to Calibre Authors parsing.
I know you can use the advanced sublist function for Tag-like (,) But I don't know if you can use it on Authors
https://manual.calibre-ebook.com/gen...-val-separator