I'm about 40 minutes in trying to figure out how to scale a rectangle to a certain dimension. I never used SketchUp. Is it also this unintuitive?
Just start typing numbers, eg. typing 5 will focus the text input in lower right corner and then you can finish by typing "5m,3.50m" - that will set the sides of the rectangle to specific exact values. Almost all tools support a similar kind of direct numerical input this way..