To edit an existing base model field:
Open the Base Model configuration (Administration > Applications > App Designer > Base Model):
Select an existing field (can be non-repeating or part of a field group), then click Edit Field. The Edit Field screen appears:
Make edits to the field as needed. You can change the display name for the field/group, or enable/disable available functionality if applicable. Other properties are disabled and cannot be changed.
Click Save to save your changes to the field.