To preview an Idle Animation in the editor, open up a dialog box for an NPC or Creature that would play the animation you want to preview. Click the Preview Full check box so that an copy of the actor is displayed in the preview window. Switch to the animation tab so that the copy of the actor is now animating. Then select the Idle you would like to preview in the Idle tree on the Idle Manager Dialog Box. The copy of the actor should begin playing the Idle you selected layered over top of whatever animation it was previously playing in the same manner that it would in game.