Query by unique username in Manage Users and Manager Assignment page

Summary:

Hi,
Currently in Manage Users page in Setup & Maintenance, the user search can only be done by email address instead of username. However, since there might be more than one username tagged to a single email address, upon searching the user account via email address, it may return more than one result which cannot be handled by our RPA program. We want to explore an option that allows us to search by unique username so that only one result appears and this is pointing to the correct account.

This issue also applies when assigning manager for an employee record, as the search can only be done by email or Name, which might appear multiple records.