I’m new to SketchUp and just finished watching a bunch of the Learn videos. I noticed in one you can select the edge of a rectangle, right-click, select Entity Info, and then edit the length of the edge.
Yes. I think you are missing something. You can draw a rectangle and type in the length and width and then change your mind and type in new dimensions IF you haven’t started a new operation.
You can use the Move tool and move the end of an edges (or corner of a rectangle) to adjust its length. In that case you would type the change in length and not the new overall length.