Comment from: amoun
To delete a slug, click on the corresponding Delete icon 
in the slugs list. You will be asked to confirm the action before the slug is actually deleted.
You should note that only user-defined slugs can be readily deleted. By default, b2evolution generates two slugs when it first saves your post (the first one will be the canonical slug and the other will be the tiny slug). If you try to delete any of them, b2evolution will inform you that the slug is related to an existing element and that it cannot be deleted without first deleting its related objects.
Important: It is possible to change the canonical slug of an Item by putting it as the first slug in the list of slugs in the Item’s edit expert form under the Advanced Properties panel. This will allow you to delete the now non-canonical slug.
For further instructions on how to perform this, please read: Managing Item Slugs.
1 comment
delete slug options.
To delete a default (canonical) slug as explained in https://b2evolution.net/man/editing-slugs-on-an-item, add another to the beginning of the line under the actual post. Although this does not reorder the list of slugs it does allow the previously undeletable slug to be deleted.