Switch modes with the mouse wheel or by clicking the label in the lower right corner; camera mode just moves the camera, room selection mode allows selecting rooms by left-clicking them, actor editing mode allows selecting actor cubes by clicking (all buttons right now) and moving them around by holding the left (left/right/up/down) or middle (left/right/into screen/out of screen) mouse button. All movement is sped up by holding Space and slowed down by holding Shift. Forgot what else has changed.
Tails19935: Hierarchy and animation editing is planned to be included eventually, but all this is still very much work-in-progress. There's not even saving yet, so... yeah.