If you would like to sort in the way you described, and following Fred's advice on changing the sort option to what is currently selected in the field 'Staff', you can sort the table in the following way:
go to your Sort tab in the table, add the following expression to the first field in the sorting list:
(the field Staff is an example)
If you add a Set statement in the expressions, you can then show all the current staff, with the current selection sorted to the first rows.
example field Hours expression:
I hope this answers your question.