A custom post status is initialized by the function register_post_status. Funnily enough, one can’t remove it by using a “unregister” or “deregister” function. There just ain’t one. There isn’t a filter for altering the registration of that status either. Or at least I couldn’t find one in reasonable time.
Manipulating the original status registration parameters happens in one way only, and it’s by using the same function on the same status again, but with whatever new parameters one wants it to be. The documentation of the function states that it’s…
A simple function for creating or modifying a post status based on the parameters given