Activate the work area by
clicking on the arrow.
Mark multiple objects with the frame.

As alternative:
Click on the yellow points of
multiple objects while the Strg- key is pressed.
All marked objects have now a
violet instead of a yellow point.
Click on the violet point to
move the associated objects.
Move single objects
Activate the work area by
clicking on the arrow.
Go with the mouse cursor over
the yellow point of the object. Click and drag.