Under the "edit paths by nodes tool" it would be nice if there was a "make selected node a square corner". (The more general tool, adjust angle to N degrees) might also be useful.) This would have two effects. The first immediate one would be to adjust the surrounding 2 nodes such that the angle into the selected node goes to either 90 or 270 degrees, whichever is closest to the current value. The second would be a property setting, such that if that node was selected later and dragged the two nodes it was attached to would move as well, so that the lines going into the square corner remain at 90 degrees. Currently with polygon shapes when I try to adjust a right angle corner it always changes angles, and I have to move another node manually to restore it to the proper angle. This is easier to do if the drawing is composed of rectangles, in which case the object can be taken apart, one or more parts resized, which maintains right angles, and the object reassembled. It would be nice if this was easier to do on a straight line polygon directly.