Is it obligatory to immediately leave a company that produces tobacco if one's work is as a secretary for the general manager and is unrelated to selling the product?

Working for a cigarette manufacturing company is forbidden because assisting in a forbidden act is forbidden. However, if the company has permissible activities and your work is restricted to them, it is permissible, though leaving is preferable. You must advise the manager to change the business activity; otherwise, you must leave the job immediately, unless there is a necessity, and delaying repentance is not permissible.