As for Final Draft 13.2.0, the Navigator has a built-in zoom function to enlarge or shrink text.
You can click and drag the zoom bar or click the - and + buttons in the bottom right of the Navigator to customize your sizing.
You can also click the percentage to the right of the bar to select from a list of preset zoom scales.
This feature is only available in Final Draft 13. If you are using a previous version of Final Draft, you can purchase an upgrade to Final Draft 13 by clicking here.