Full Outer Join in MS Access
The last time I played with Access was when 2003 was the hot new thing, so this may not be entirely accurate to every detail. However, what you need to do is go to the query designer, change the view to "SQL" (i.e. raw text entry) and then you want to UNION your two left-join queries together, e.g.

SELECT ListA.*, ListB.*
FROM ListA LEFT JOIN ListB ON ListA.[StaffID] = ListB.StaffID
UNION
SELECT ListA.*, ListB.*
FROM ListB LEFT JOIN ListA ON ListB.[StaffID] = ListA.StaffID