Fully customise the permalink for an individual page or post and globally set the permalink structure for pages, categories, tags or authors.
If you have not enabled custom permalinks (Settings > Permalinks) and they are set to the default option, the plugin will not recognise that custom permalink structures are enabled.
A permalink alias is an additional permalink value that can be set to redirect to the actual permalink.
If a user enters the URL of an existing alias value, it will header redirect (301) them to the correct location.
Customisepermalink button on the admin edit screen.
OKand update the entry to apply the changes.
The default permalink structure will then be applied.
Permalinks should by unique across your site, if you are trying to define a duplicate a numeric value will be appended to the end.
For example, if there is an existing custom slug of "/post.html", it will be turned into "/post.html2".