A FUSE (Filesystem in Userspace) developer designs and implements custom file systems without altering kernel code. They leverage the FUSE software interface to communicate between the kernel and user-level file system. They create, read, write, delete, and manage files and directories, and handle permissions and security. The developer also troubleshoots and optimizes the performance of the file system. They collaborate with other developers, sharing knowledge and integrating their work with other systems. Their role requires a strong understanding of Linux, C/C++, and file system concepts. They must consider factors like data consistency, recovery, and user requirements.