The Composite Application Editor team was very busy in the Notes 8.5 release. One of the highly requested features made it into the tooling. This new feature is the Property Value Editor. The dialog can be accessed from the Composite Application Editor menu under Edit | Property Value Editor.
The dialog is very powerful. You can filter what properties you see based on a criteria (preference name contains or preference value contains). You can then do global changes to those properties from the dialog in a single action. This is a great feature for doing widespread search and replace for page and component property values.