To ease out the data entry while recording the Patient Encounter, ERPNext Healthcare allows you to save every Complaint / Diagnosis data you enter as a Master, from the Patient Encounter screen itself. This way, the database keeps building a list of all complaints and diagnoses you entered. This is done for better analytics and reporting.

You can also configure the masters manually by going to,

Home > Healthcare > Consultation > Complaint

Home > Healthcare > Consultation > Diagnosis

You can then select the Complaints and Diagnosis in the Patient Encounter Screen: