By default, all vectors are displayed with the same line width, regardless of their actual line width.

To turn line width display on or off, do either of the following:

Press Shift+L.

Select View Menu > View Vector Line Widths.

The line width is displayed in pixels.

You will only be able to see line widths when you are viewing vectors by color. To toggle between viewing vectors by color and by type, press your C key.

You may need to zoom into the image before you can see the line widths.