Is there a way to perform a secondary sort of records in AD Ediscovery or Summation Pro?
Yes. This can be done in the "Item List" grid.
1) Open the Item List.
2) Sort on first column (i.e. primary sort).
3) Hold down the "shift" key and then, left-click on a second column (i.e. the column to be used for secondary sorting).
Note: Further "shift + left-click" on additional columns would add additional sorts to records in the item list (i.e. tertiary sort, etc.).
Additional Note: For best results, add fields containing a single value to secondary sorts. A checkbox (multi-entry) field included in such sorts will give varying results if any records contain more than one value in that multi-entry field.