NullEditButton adds a "Null Edit" option to page controls. A "Null Edit" is in a way similar to purging, but better. It forces the server to rebuild the page using new data.
Advantage
All other purge methods do not apply to categorization and what links here changes from template edits, but a null edit does.
The properties, filterable lists, etc generally require a null edit to get the data updated.
A normal ?action=purge doesn't usually work.
Very useful for DPL forums where a purge wouldn't work.
The button
The button is added to the drop-down besides the Edit button. In case the arrow doesn't exist like while viewing diffs, the null edit is added below Back to page link instead.