Mito's dataframe difference functionality lets you find unique records across two different dataframes. You can access this functionality on the Home tab, by select the Merge dropdown and then selecting Anti Merge.
Finding unique rows between multiple datasets.
Unique in Left: Includes each row from the first sheet that doesn't have a match in the second sheet.
Unique in Right: Includes each row from the second sheet that doesn't have a match in the first sheet.
Just like the other types of merges, Mito uses the merge key that you select for each sheet to detect matches.