Output window I've only seen have output in it when messing with AI encounters, like telling you how many firing points a squad has.

The four buttons change the mode Sapien is currently working in. The first one is your normal editing mode, the second one is a lightmap editor (which is broken afaik, it can't save your changes), the third button is a scripted camera editor which is good for laying down camera points for cutscenes (press the spacebar to set a camera point at the current location and rotation of your camera) as well as recorded animations (had the ability to control units in Sapien been left in :argh: ), and the last button turns on a model viewer; select a model and it's placed at the level origin (0,0,0), and then you can check all of its animations, permutations, and LODs.