Can a script be made to allow several employees to add to a requisition, and the approval happen by line? Then allow one final approval by purchasing before sending to the supplier?

the Approval Status field is a header field.

If you can add a custom column to that sublist, it’s a possible. You will track ‘Approval Status’ of each line and only when all lines are ‘approved’, the header field “Approval Status” and the status can be approved.