As per our EMR certification requirements, there is another field for "Gender Identity" on the Patient Demographics screen:

If you want to select “Unknown” for Gender which is a required field, you could then populate the Gender Identity field.

NOTE: Selecting Unknown will cause the patient to excluded (not counted) for the UDS Report "Patient by Age and Gender" However, the patient would be included (counted) in the "Patients by Gender Identity" UDS Report. 

There is also an additional field under “User Defined Fields” for Patient Birth Sex, after selecting be sure to select the “Save” button