...
You cannot add new properties through this page. To add new properties, you will need to add them to the case management sections for your application. For more information on case management and adding saving data as case properties, see https://dimagi.atlassian.net/wiki/x/hB3Kfw.
Metadata is read only and cannot be altered. For more information on metadata, see these two documents: https://dimagi.atlassian.net/wiki/x/i0nKfw and Metadata Glossary. Case names are also read only.
You cannot edit properties that were added via a case import but are not part of any application. Easy references in the form builder have a similar limitation, where properties created via case importer are not recognized. To work around this, you can create a "fake" form as described here.
If your project space uses location restrictions, you must give users the "Full Organizational Access" feature in order to use the Case History and Clean Case Data features.