HCM Communicate - Token with Known As

We need to have a token for 'Known As' in Communicate, and if there is no 'Known As' filled, it should use 'First_Name'. Alternatively, this condition can be handled directly in the 'First_Name' token, prioritizing 'Known As' and defaulting to 'First_Name' if 'Known As' is not available.
This customer values diverse communication practices and prefers using only first names in their email communications. Using the "Full_Name" works because it shows the Display Name in the message (Display Name is configured to exhibit "Known As" OR "First Name" + "Last Name"). But using the First Name token it shows their birth name.