ALREADY EXISTS! When a user wants to send a document for review or approval it would be great if the user can search for a name in the "Document Workflow - Start Review" and "Document Workflow - Submit for Approval" dialog, because that list can be very long.
This is a correct observation. The search filter becomes available when more than 20 reviewers or approvers are available in the list.
The missing search option was in our NFP environment. In Production we have the filter functionality available. It is probably shown from a number of people.