In Workbench's Visual Preview window it would be handy to be able to search/filter the table values by null, missing, empty. These null values are available in the Filter for the Graphics View, but not in the Table View search box. If available, this would allow a quick count of features that have missing values in a particular attribute field/column.
This functionality would have come in handy during the Desktop Basic training for Best Practice - Exercise 1 during step 4 when you confirm that the CrimeValue attribute is missing values on some of the features. If you could filter the CrimeValue column using a '<missing>' value, then it would easily confirm the number of features missing a value (instead of sorting the column and scrolling down the table see which row numeric values start appearing).
The same would apply to Data Inspector.