Let's say that I am looking at my agenda view (C-c c a), where I usually mark items as DONE from there (by pressing 't' several times to run through all statuses). The thing is, the fist status is TODO and the last DONE. But how to set a CANCELLED status, for those that have been cancelled without having to delete it or mark them as DONE (which is not true)? Thanks!
You can create a "CANCELED" state that is in a sequence by itself and that counts as
(setq org-todo-keywords '( (sequence "TODO(t)" "NEXT(n)" "STARTED(s)" "|" "DONE(d)") (sequence "|" "CANCELED(c)") ))
This gives you, essentially, two independent
DONE states, neither of which will appear in the agenda todo lists.