This file is available only for the panels created using the panel merge feature or the Delete and Save option for a custom panel. It lists the amplicons that were dropped from the parent panel to create the new panel. The amplicon IDs in this file are from the source panel or the parent panel.
For RNA panels the file contains the list of user-submitted amplicons that were dropped as they conflicted with the DNA amplicons. It shows the full amplicon details along with the conflicting DNA amplicon ID. See the example below: