The slug is a unique identifier used to distinct the posts and terms and used in the native (default) permalinks that can be overwritten by custom permalinks set-up with Permalink Manager.
The slug is assigned to the post or term after it is published and it is based on the initial post/term title. Please note that it remains unchanged even if you change the post/term title. Of course, you can still adjust the native slug in the slug editor.
As Permalink Manager stores the permalinks independently, you can change each of posts or terms URL addresses any way you like. It does not matter if your new permalinks contain the native slugs or not.
How to edit the native slug with Permalink Manager?
Please follow the below instructions, if you need to edit the native slugs for any reason. To display the slug editor directly in URI Editor included in Permalink Manager please enable ‘Show “Native slug” field‘ in Permalink Manager settings: