How to maintain enums (and adding new values) in a very large codebase

In a very large and old codebase, suppose we’re using a database column status with enum values as NEW, IN_PROGRESS, COMPLETED, REJECTED.

Now this status is used in multiple conditions in code like

if (status == `NEW` || status ==  `IN_PROGRESS`) {
  // do something
}

or might be in some SQL statement like

WHERE status NOT IN ("REJECTED")

Now if we want to add a new enum value to status eg. “CANCELLED”, then we’d have to handle all the places where status was used in the code.

Considering that the codebase can be somewhat distributed, large and quite old, it would prove to be very difficult for this sort of change. How can we improve this such that it would be easier to maintain these sort of changes?