What is the Entity Status field in the Criteria of an Item Saved Search?

Hi,

On opportunity records in NetSuite there appears to be 2 status'. One of them is "Document Status" and appears to be standard in Netsuite and is auto populated based on some pre-defined criteria (see red box below on screen shot), the other appears to be called Entity Status (see yellow box on below screen shots).

In "Customise Form" page:

For clarity - the options for the field highlighted in yellow on the above (Status / Entity Status) are set in the "Customer Status List", shown here with navigation also shown:

On to my question - I can't find the field which is referred to as "Entity Status" in the criteria on an "Item" Saved Search, I can find loads of other transaction and customer fields, but not this field that is critical to our sales process! Some screen shots of the transaction field options that I can find are here (based on the field being called either "Entity Status" or "Customer Status":