I want to sync my read status in caliber with my Kobo Auro H2O(Koreader) but it is not supported yet so the advice here is to create a read status column then sync the data to it.

Can anyone explain how to do it?
Caliber has the option to add custom columns. The option is available trough Preferences -> Add your own columns -> Add custom column.
The complete procedure is explained in this article: does it fit for you?