The "SSL trust store password" Parameter Field as well as the "SSL trust store location" field within "New Authentication System" interface cannot be updated from a prior configuration. The values that are in place are locked and cannot be modified.
This is expected behavior of the product.
Once an Authentication System has been added to the configuration, the settings related to SSL are non-editable fields in Desktop Client. However, these can be updated through the use of the setdbparms command utility that exists on the DE manager server(s). If you are taking advantage of HA functionality in your environment, then you will need to make this change on both the primary and the standby servers.