I was used to use Sketchup on Mac but I recently changed my computer, and I’m now corking on Windows.
Since I can’t modify the dimensions when I’m creating a rectangle (or any other entity).
Please describe the exact steps you are trying to use when modifying dimensions. It does work on Windows.
I think you’ll find that no matter how many times you try reinstalling SketchUp, that won’t change it. It must surely be with your procedure. Are you clicking in the Measurements box before trying to change the dimensions? If so, don’t. Notice in the GIF my cursor never goes to the Measurements box.