Can I change my job title from "Director" to something more modest?

No. Use the title you actually held. Changing a title to make yourself look more junior is still a false statement, and it can be uncovered in reference or employment checks.

What you can do honestly:

• Keep the real title and make the bullets focus on hands-on work you did.
• Add a short clarifier in brackets if your title was unusual or inflated. Example: "Director (small firm; team of three, hands-on in all client work)".
• Describe the scope accurately, including how much of the work you did yourself.
• Use your summary to explain the role you want now.

Employers mostly worry about what an impressive title implies, such as high pay expectations. Explaining the reality of the role and your current goals answers that worry far better than a changed title.