No, it's usually much quicker to edit the plot file that came out of ODLEDIT the first time you ran it. If you want to change the scale or slab, go to the top of the file and look for the following two lines:

 scale 2.200000

 slab -15.00000 15.00000

and change them to suit your needs. If you want to change the Z-thickening, go to the bottom of the file, and look for lines:

 zthick 0.3000000 0.2000000

and change them there.

Then you can just feed the altered plot file into oplot again and watch the result on the screen.