Parallax tab is actual for Stereo project type.

Use this tab to see left and right frames of a stereo pair, overlapped upon each other.
Set foreground and background parallax values moving the frame with the mouse. Match frames by the closest object to set the foreground parallax, and set the background parallax by the most distant object.

Use the Autodetect checkbox for automatic parallax setting.


Also it is possible to call the Auto detect parallaxes command from the context menu (right mouse button) for the scene in the Timeline