For example, you want to remove certain Gift Appeal IDs but keep Gifts without an Appeal ID:
  1. Go to Report > Selection Formulas > Record
  2. Enter the formula: isNull({GfApls_1.GfApls_1_Appeal_ID}) or {GfApls_1.GfApls_1_Appeal_ID} <> ["x", "y", "z"]
  3. Click Save and Close
  4. Refresh the report