Board Thread:Support Requests - Getting Technical/@comment-5693502-20170403182620/@comment-2200849-20170405180251

Andrewds1021, all MediaWiki messages starting with Custom-* are whitelisted for editing. The reason there is no documentation is because these messages were whitelisted so that people can write custom scripts to use them, so the exact "instructions" depend on the script and its use cases. For this particular page, the script that uses it is w:c:dev:WikiaNotification.