Changed objects which has not been yet saved into a Project File or Project Folder are displayed with change indicators in ID column.
You can check history of changes for the selected object in the History Pane using View > History Pane menu or using CtrlAltH shortcut.
You can maintain suspect link flag to propagate changes of high level objects to the downstream objects linked by traceability links. A link becomes suspect if its target object changes. A suspect link is displayed with icon:
For more information see Section Suspect Link Flag.
When the project is saved, you can choose whether to save the project history. You might want to save project as a new project baseline stored as a Project File or Project Folder with clear history.
You can store ReqView files under a version control system (such as SVN, GIT or Mercurial) to baseline document revisions and to manage requirements together with source code and other documents.