There are many reasons why a custom link may need to be deleted or changed. Most commonly, a custom link may be created by an admin without assigning it to a segment only to realize later on, that it is not possible to add a segment to an existing custom link.
If you have already made last-mile translation edits and are concerned about losing your edits if you remake your custom language link with a segment, we can assure you that last-mile translation edits will be retained/preserved.
The newly added segment will not retroactively track link visitors. So it's important to make this adjustment as soon as possible.
In the image below, you can see that a custom language link has been created with no segment assigned to it.
You can click on the Red trashcan highlighted above to delete the custom language link.
Now in the image below, you can see a second custom language link has been created, this time with a segment assigned to it. As an example, this segment is titled Spanish Speakers.
The custom language link with no segment associated with it can now be deleted.