There is a Portal Parameter cp_knownas_description that controls if 'Known As' column is used in place of employees Forename column.
Please set it to Y and test in UAT.
Steps:
Portal
Go to Administrator Dashboard
Admin Tools
Within Site Manager Open Admin Settings
Search for cp_knownas_description
Edit, Set to Y
As of this patch 28.0.122 it is now possible to use and search for employees based on their "Known as" name.
This new option can be enabled via a parameter within the administrator dashboard. Please follow the below instructions to find this parameter.
Got the administrator dashboard
Find Site manager widget
Select admin settings
Search for "cp_hradmin_knownas"
Click edit
Set the parameter to Y
Click Save