What goes in a column
So far a new column has been arithmetic on the ones already there. This part is about everything else you can put in one.
Text you need to clean up. A number that arrived as text. A date you want the year out of. A category that depends on a condition. A value that is missing, which is its own subject and gets a chapter.
Every one of these is written the same way, inside add or summarize, so there is no new grammar in this part. There are only more words to write in a place you already know.