Hi Jason,

>>>but I can not just modify object's size with width or width

If you are just trying to change an object width for example, then use the scale 1d. Click on the first corner, then let the cursor snap to the other corner, if you then check the readout at the bottom of the screen it will show you the current size (d) :-



then left click the corner, and move the cursor, you will see the readout change to show the current size.



You can also click in that little window (d) and input a size.