No - as you newer know when the payment will be made. Invoices are posted and “forgotten”, nothing more to post there. Payment can occur substantially later, even in another accounting period, so even theoretically you can not post gains/losses back-dated, it will change balances of probably closed periods.
FCY gain/loss is directly related to PAYMENT (and it’s date), not Invoice, so Navision does post it according to accounting rules.
Unrealize Gain should hit Outstanding Invoices , where their values changes and hit AR as well, so Cust. Ledger Entry updated at Invoice.
Realized Gain should not hit Invoices: for
Realized Gain value the differences between Original Rate and Closing Rate*. (where we “fully paid / matched” the invoices)
It’s no more Outstanding Invoices ( It will not be Realized until an outstanding invoice get matched / closed ).
It has no impact on AR. AR amount closed with last booked rate, the closing ex.diff goes to income/expenses directly.
(otherwise, you would have an extra unrealised gain/loss , then carry them all out , then book realized with an over-stated amount.