Document management approval status where value = null

On the Document Management\Approvals screen in Aurena, we are trying to clean up the list of entries to show just the records with a null Approval Status...ie those that are waiting for an approval or a rejection. 

We can see these entries when the full screen is populated. But we cannot filter for null or not eq rejected or approved. 

Is there any way to do this filter? 

Our current version of IFS is 
 

Thank you,

Lorraine