if you take a look at this article where it says you cannot build a collection view of another collection, this is pretty much what you are asking to do. You're building a report, and pulling in a collection of documents to report on.
Anything you put into your valueexpression should be coming from the fields tab or the references tab at most, in the API explorer. However, the information that you are trying for, would be stored in the document version (and document versions are a collection in every document -- hence collection of a collection in this case means you're trying to build a view by pulling in a collection of documents each with a collection of document versions that has the information you seek). Hope all that makes sense.
Normally at this point, the only way to get this information is to go at least one level down. You can make a document report, and pull in the collection of document versions for the information you seek. Or you can make a document version report and not have to pull in any collections.
https://experienceleague.adobe.com/en/docs/workfront/using/reporting/reports/text-mode/reference-collections-report#limitations-of-a-collection-view