try changing one in the demo company.  Screen shot a part and then do the  rename then relook at part. you will have to move off the part for the "update" to show

Its in I/C Utilities maintain Productline

USE the A->B button on the tool bar, its the rename

That is correct.  the A>B button is used for Renaming any ID.  FYI - The rename button is is available for all IDs and not just Product lines (customers, vendors, parts, etc...).