The ruler is located on the edge of your screen at the upper right in the Query Painter. It is switched on in the standard.
You can hide or re-display the ruler on demand by using the appropriate pushbutton.
To set list width, proceed as follows:
Place your cursor at the right end of the ruler. Once the frame appears, expand or contract it to the width you want. Alternatively, you may directly enter list width in characters in the List Width field located in the lower left-hand part of your screen.
If you want to decrease list width so that it is smaller than the combined width of the fields on it, overhanging fields are inserted in a new line.
If you want to frame your list, select the checkbox List with frame.
Your list must be framed if you want to use field separation.