Nudge configuration - User Eligibility Profiles

When configuring Nudges, it allows us to define whether the employee or manager group will receive those email nudges. How, if possible, are we able to further define the eligibility of the groups that receive those emails.

The Employee and Manager populations are predefined fields and we don't see if we're able to update the list of values to include anything additional.

Does anyone else have any experience with this specific scenario or would be able to shed more light on the issue at hand.