It really depends on how the dimension is currently setup and what methods you are employing. Does the additional column need to take part in change tracking?
If so and you don't want to add a new row (which would seem to be correct if change tracking is necessary (E.g my dimension has column X, yesterday it was blank but today it has a value, therefore is a new row) then it appears the only option is a manual one.
Adding a column that doesn't take part in change tracking is a common scenario and should be relatively easy.
If you expect more columns that do take part in change tracking over time, I would be questioning the design of the dimension itself......