Custom URLs now redirect users to your new URL that is based on your handle. If you need to change your URL, you can do this by updating your handle at youtube.com/handle.
New customised URLs can no longer be set up and existing customised URLs can no longer be changed. Existing customised URLs will continue to work. If you must permanently delete your customised URL, you can do so by deleting your channel. As a reminder, deleting your channel is a permanent action.
If you'd like to create a new URL for your channel, change your handle. A handle URL is created automatically whenever you choose or change your handle as a channel owner. They display as, for example, youtube.com/@youtubecreators.