From Synfig Studio :: Documentation
The "Focus Point" parameter is present only in the Group Layer layer. It has a Vector value. It defines which point in the grouped layers will stay still as the Group layer's Zoom Parameter changes.
The Focus Point is relative to the Group layer's Origin and defaults to (0,0) so its handle will be hidden behind the green Origin handle initially. Its handle can be seen by turning the Origin handles off temporarily (by hitting Alt1) or by editing its value to something small by non-zero in the Parameters Panel.
It's best to edit the Focus Point parameter while the Group's Zoom is set to 0. Otherwise you'll be seeing a scaled version of the contents.