A Final Cut Pro X developer designs, develops, and maintains the popular video editing software, Final Cut Pro X. They write code, fix bugs, and improve the software's performance. They also design new features and enhancements to meet the needs of users, such as filmmakers and video editors. They work closely with UX/UI designers to ensure the software is user-friendly. They must also test and debug the software to ensure it runs smoothly. Furthermore, they constantly update their knowledge about new programming languages and technologies to keep the software relevant in the fast-paced digital world.