The "Focus Point" parameter (added in SVN r2290, not yet released) is present only in the Paste Canvas layer. It has a Vector value. It defines which point in the encapsulated layers will stay still as the Paste Canvas layer's Zoom Parameter changes.
The Focus Point is relative to the Paste Canvas layer's Origin Parameter and defaults to (0,0) so its duck will be hidden behind the green Origin duck initially. Its duck can be seen by turning the Origin ducks off temporarily (by hitting ALT-1) or by editing its value to something small by non-zero in the Params Panel.
It's best to edit the Focus Point parameter while the Paste Canvas' Zoom is set to 0. Otherwise you'll be seeing a scaled version of the contents.