It would be very helpful to be able to open multiple ReqView windows of the same document tree (project) at the same time, with all windows either showing the same document, or different documents.
Use case 1: requirements production/refinement.
For example using a customer specification as the input document, and writing a software requirement specification according to it. It's very unwieldly to not be able to have both open side by side.
Use case 2: creating links.
Have the source and target documents open side-by-side, and selecting source in one, jumping to the other, selecting target. Or, even better, drag-and-dropping between the windows to create link relationships.
Use case 3: working in different locations of the same document
E.g. inspecting different chapters of a document, making sure that all necessary topics are covered.
Those were my preferred workflows in DOORS.
We planned this feature for ReqView v3.