Well, thank you for the help. I did try to find previous answers, but I limited the search and did not search this forum. So I would not have found the (your) other answer.
So the remaining records are now inserted and the Column Controller seems to be working now. My modifications to column_left.php and column_right.php are gone, of course; I expected that. So now I have my columns reset to the defaults and now I can proceed to modify the columns using the Column Controller. The Column Controller is under the Administration Tools, so as I said, it seems to be working.
This contribution does add some useful flexibility. I wonder if it can be generalized further; I see that there is coding that is specific to each box that perhaps could be generalized somehow. That is another possible project for me to add to my long list of things to try.