The "Regenerate/reset" function is most usually used to make the permalinks adhere to the default formats specified in the permastructures settings. This functionality may be very helpful if you need to quickly update the permalinks of certain post types or taxonomies items.
How to regenerate the custom permalinks?
To open "Regenerate/reset" tool and regenerate existing permalinks, go to "Tools -> Permalink Manager -> Tools" section. Please pick "Regenerate custom permalinks" from the first dropdown ("Mode"). Then, depending on the content type, pick either "Post types" or "Taxonomies" in the "Select content types" section.
Depending on your requirements, you may run the tool for different post types ("Select post types") or taxonomies ("Select taxonomies") at the same time. Using the "Select IDs" field, you may also target just particular posts or terms. Finally, to start the process click the "Regenerate" button.
If everything went properly, you should see a list of updated permalinks displayed below the form.
How does the "Regenerate/Reset" tool work?
To put it simply, whenever the URI is regenerated, Permalink Manager will replace the currently used canonical permalink (see "Current URI" below) with its default version based on current permastructure settings (indicated with "Default URI" field).
If necessary, you may manually examine the process's result using URI Editor.
The "Restore Default URI" button in the individual post editor and the "Regenerate/Reset" tool both perform the same thing, which is to change the "Current URI" value to the one specified in "Default URI".
How to exclude custom permalinks from "Regenerate/reset" tool?
You may exclude certain permalinks from processing in the "Regenerate/reset" tool if you manually modified them to avoid accidental overwriting. In order to do this, under the "Auto-update the URI field" section of the URI Editor, choose "No (ignore this URI in bulk tools)".
How to automatically update single permalinks?
You can find more detailed instruction on this here.
How to regenerate native slugs?
The procedure is similar to the "Regenerate custom permalinks" mode. The new native slugs will be created from a single post/term titles. In this mode, you will be unable to restore the original slugs unless you have a database backup.
To begin the process, pick "Regenerate native slugs" from the "Mode" option field. Then, you must specify which post types and taxonomies should be affected.