Unable to rename fields in advanced search using page composer

Summary:

Hi,

We have a requirement where business user generates a performa invoice number for few shipments in a custom VBCS page. Requirement is to update the performa invoice number on manage shipments page screen in a field, so that they can search using it and then mass ship conform the selected shipments with same performa invoice number.

I have found a field Dock which is editable and currently not being used. I have renamed the field as performa invoice number. This field appears as a criteria in the advanced search. But I am not able to rename the field in advanced search area. It still appears as Dock. I am unable to rename it using page composer.