The "Custom Delete Codes" Query allows you to specify records that should be deleted. These records that should be deleted should not also be provided by the "Source" Query (within the current running of the source scanner). But the records to delete may fall outside the scan range, and, in fact, they usually will fall outside the scan range.
Read More > "Source" Query
Read More > Scan Range Minimum/Maximum
As an example of when this might be used, consider a system for tracking donations. You may be rescanning donations by the current open period, and you may be only reporting on unreversed/uncorrected donations in the "Source" Query. If you later reverse and correct a donation originally entered in a past period, and if this reversal and correction are associated with the current open period, you would need a way to specify that the corrected donation in the past period should now be deleted.
Remove the check next to "Use Template" to allow custom editing.
Press the <Edit> button.
Read More > Using the Query Designer