Do a find, then open the Folder Options dialog and add the column there. Then, in the same dialog, use Save > For This Folder. That will ensure it is saved for the folder you are currently viewing. (The steps are similar to #1 in Folder Formats: Quick Guide, which has some screenshots to help; but you want to only save the change for that folder and not for all folders.)
The column should also be added automatically on new configs or when folder options are reset, but may not be for configs imported from older versions.
We've also improved this a bit in Opus 12, if I remember rightly. It will add the column automatically in more situations than before.