Allows the selection of a single order for all tasks which operate on an order-by-order basis. For example, to re-fit the order trace for order 3, leaving all other orders as-is, first use this option to change the Selected order to number 3, and then invoke the ech_fitord option.
Note that any options which operate on all orders at once (e.g. trace consistency checking) will still operate correctly when a single order is selected, as they ignore the selection and use all the orders anyway).
Martin Clayton