Archived matters do not appear on the list of all matters but rather hidden (Archived). The same archived matters can be visible to only you and some other few users or be visible to all users depending with how it was set.
To manage archived matters, first filter the search to locate them. On the corporate matters go to Advanced and then More Filters Criteria and on the Archived field choose Yes to show archived matters. Then click Submit
You can then click the Save as Button to save the filter for feature. The filter name will be added on the label beside the Save as button
Use the Hide button on the far right to hide the search filters
An archived matter can be opened and be viewed, unarchived or deleted etc.