Add arbitrary metadata to a column

Is it possible to add metadata to a column in harmony 22?
For specific scripts in our internal pipeline we would like to get information froma column. If you are not able to add the metadata to a specific column, I was thinking of adding text to an annotation column and extracting it to get the data that way. If possible, how do you add/extract data to an annotation column through code?
I am pretty new to harmony.