The Revenue Commitment is at the line level of the sales order. Therefore, Main Line equal to True filter should not be added to the search. The Created From field has a NULL value at the header level.
-Navigate to Reports > Saved Searches > All Saved Searches > New
-Click on Transaction
-Search Title = type a title for search
--Type = Revenue Commitment
--Main Line = False
*Add or remove fields as required.
-Save & Run