The built-in permalink system in WordPress is quite simple and straightforward to use, but it falls short when you need to create more advanced URLs formats or when you need to tweak a single permalink.
While you can easily edit the slug for any post or category directly from the content editor, and modify the base structure for categories or tags in the Permalinks settings, these built-in options are often insufficient.
Permalink Manager can fill that gap and unlike other permalink plugins, it gives you complete control over any custom permalink. This may be helpful if you want to change the format of some of your permalinks from the default predefined formats.
Once a URL is changed, the plugin automatically redirects the old address to the new one using a canonical redirect, preventing 404 errors that can be harmful for SEO and user experience.
How to Access Permalink Editor?
Classic Editor
To display the URI Editor simply click on the "Permalink Manager" button (just below the post's title). You can modify the individual permalink in any way you wish, as shown in the example below.

Until you manually adjust it using the "URI Editor" the initial URL will be based on the generic permalink format (given in the "Permastructures" section).
Block Editor (Gutenberg)
If you are using the Gutenberg editor, you will notice that the URI Editor is located in a different area in the UI. You can access the URI Editor on the admin sidebar, as shown in the picture below.

Category & Custom Taxonomies
Permalink Manager allows you to edit permalinks for individual categories and custom taxonomy terms. This works not only for WordPress’s built-in taxonomies, such as categories and post tags, but also for any custom taxonomies you have registered.
Managing permalinks for categories and custom taxonomies works the same as managing post permalinks. The permalink editor is accessible from the "Edit term" page, so you can change the URL directly where you edit the term's title and details.

How to Change Permalinks in Bulk?
In order to speed up the URL changing process, the Bulk URI Editor allows you to alter multiple permalinks at once. To access it from the WordPress admin dashboard, use the sidebar and go to "Tools -> Permalink Manager".
Using the editor, you can review and bulk edit permalinks for different post types and taxonomies separately, as shown in the screenshot below:

How to Prevent 404 Errors?
Broken links can negatively affect both user experience and search performance. Permalink Manager uses automatically redirects the original WordPress URLs to the new ones, so visitors and search engines do not encounter 404 errors after a permalink change.
This helps to preserve link authority and allows search engines to recognize that content has moved instead of being removed. If necessary, in the "Manage redirects" section, you may additionally define extra URL redirects.
Troubleshooting
Why Can Not I See the URI Editor?
If the URI Editor does not appear in the interface, there are two main reasons for this. This can occur if your post is saved as a draft and the "Exclude drafts" option in the plugin settings (in "Exclusion settings" section) is enabled.
Another possibility is that the item's post type or taxonomy is excluded from editing in the settings. Similarly to the first example with "drafts" deselect the post type to allow Permalink Manager to control their permalinks.
How Can I Exclude Particular Content Types?
By default, Permalink Manager saves custom permalinks for all public post types and taxonomies. There is no need for this in many cases, for example, if you only want to change permalinks of one single post type (e.g. products).
You ought to consider this if your website has more than a few thousand pages. If this is the case, it could be a good idea to exclude post types and taxonomies that do not require URL adjustments.

Deactivated “Custom Permalink” Field
If you use "Auto-update permalinks" mode in the plugin settings, your custom permalinks will be updated every time you change or save the post or article. As a consequence, any manual adjustments will be replaced with the default format of custom permalink depending on Permastructures settings.

Editing the URLs makes no sense because any manual changes will be overwritten by the default address provided in the "Default custom permalink" row. As a result, the "Custom permalink" field will be grayed out and set to "read-only" mode to minimize user misunderstanding.
An in-depth explanation of the "Auto-update permalinks" function may be found in a separate article.