Luis Peel

This plugin provides a simple and powerful interface for managing custom post type slugs. With it, you can:
<ul>
<li>View: See a complete list of all custom post types registered on your site.</li>
<li>Edit: Quickly and safely change the slug of any custom post type. For example, you can transform “vehicle” into “car” for shorter and more descriptive URLs.</li>
<li>Delete: Completely remove the slug of a custom post type, simplifying your URL structure.</li>
</ul>
Example:
If you have a custom post type called “vehicle” with a URL like <a href="https://www.yoursite.com/vehicle/mycar" rel="nofollow ugc">https://www.yoursite.com/vehicle/mycar</a>, this plugin will allow you to change the slug to “car” to get the URL <a href="https://www.yoursite.com/car/mycar" rel="nofollow ugc">https://www.yoursite.com/car/mycar</a> or even remove it completely to have <a href="https://www.yoursite.com/mycar" rel="nofollow ugc">https://www.yoursite.com/mycar</a>.
Benefits:
<ul>
<li>Greater control over your URLs.</li>
<li>Flexibility to adapt URLs to your specific needs.</li>
<li>Ease of use thanks to its intuitive interface.</li>
</ul>

Custom Post Type Slug Manager

Easily edit or remove slugs for any custom post type. Customize your content URLs without coding.

texttheater

NOTE: recent WordPress versions already properly transliterate umlauts if the 
site language is German. In that case, German Slugs is no longer needed.
While creating a post or page, WordPress automatically suggests a permalink. If 
your permalink structure contains the %postname% tag, then the title of your 
post or page will be used, simplified by conversion to lowercase, replacing 
spaces with hyphens, removing certain punctuation characters and removing 
diacritics from latin letters.
Thus, by default, ä is replaced with a, ö with o, ü with u and ß with s (similar 
for capital letters). For German, the conventional transliteration is ä to ae, ö 
to oe, ü to ue and ß to ss (sometimes sz in Austria, this is not yet supported). 
This plugin makes your WordPress apply the conventional transliteration.
I wrote this plugin because manually correcting WordPress’s suggestions is a 
considerable hassle, especially if you decide to change the title afterwards.
<h3>Support</h3>
If you have questions or suggestions, contact me at poststelle ät texttheater döt 
net.

German Slugs

German Slugs properly transliterates umlauts and the letter ß appearing in titles for slugs (i.e. for pretty permalinks).

Custom Post Type Slug Manager vs German Slugs