[Lynne]

I *think* it is. I am pretty sure I did it that way on my site, but my site is so modified that I really can't post the plugins. These are the hooks I used (and some may be related onto to the mod I wrote and not just making the column):
forumdisplay_complete
forumdisplay_announcement
search_results_prebits
search_process_fetch
search_results_threadbit
tags_list_threads
threadbit_process
threadbit_display
threadbit_display

If you search through the code for those hooks, then you may be able to figure out what was done. If I recall, there is a variable that sets the number of columns and so I had to add 1 to that variable in order to add the column (in multiple places).