Customizer Plus allows you to create a WEDD resource which allows you to lock a particular structure file to a particular data file. This is known as "wedding" and is used to prevent the use of old or incompatible files. By default, there is no WEDD resource installed in the structure or data file.
If you click the grayed out WEDD icon and click 'OK' to the message asking to create the resource, there is no way to remove it in Customizer Plus. If you have the need to remove it prior to 4D version 6, you would have to use a resource editor such as Resedit or Resorcerer.
In version 6, you can delete the WEDD resource via the following 4D code:
$ResFile:=Open resource file("")
CLOSE RESOURCE FILE($ResFile)