Hello, any one know how i can un-apply a customer payment that has generated a currency revaluation without deleting the currency revaluation. Currently the system will automatically delete a currency revaluation when a payment is unapplied to an invoice. However if a period is closed the currency revaluation should not be deleted, it should be reversed Thank you

This is not an answer, but a headsup: If the user who unapplies the customer payment, and the CP and CR is in a closed period, AND the user role has ”full” permission for CR, the CR will be deleted from the closed period.

You cannot, these are two sides of the same coin so to speak. To reverse the application you need to issue a credit memo in your open period.