But why do you need columns at all? To set the width of the 1st column? Simply adjust the DefaultColWidth. Depending on whether the option doKeyColFixed is in the DisplayOptions the first or second column will be adjusted automatically to cover the rest of the control (provided that doAutoColResize is in the DisplayOptions).
The reason I was trying to access Columns is that TValueListEditor did not work as I wanted at design time.
Now it works as you mentioned. But the order of setting properties matters. It finally worked when done in following order (during design time):
1) FixedCols=1 (Probably I might have missed this in the beginning).
2) DefaultColWidth=120
3) doKeyColFixed=True
4) doAutoColResize = true
If I check doAutoColResize before doKeyColfixed then the two columns become the same size. And then the size of Key column is fixed, regardless of DefaultColFixed.