Revit has previously enabled the following dialog windows to "dock" or "stick" to the left, right, top, and bottom of the Revit Application Window.

The following windows can be moved and resized, and either floated or docked:

•  Project Browser
• System Browser
• Properties palette
• Reconcile Hosting window

They can also be grouped so that several windows (represented by tabs) occupy the same space on the screen.

  In Summary:  Use tabs to work more efficiently with a familiar workflow for dialog windows.