I have experience as a gifted education teacher/coordinator. Can my experience substitute for the practicum?

You will still need to take the practicum course. The practicum is the last course in UNI's four-course sequence for the endorsement. During the practicum you will apply the concepts learned during the three previous courses. You will also participate in other new activities and apply these to your teaching. Although your prior experiences with gifted students will undoubtedly assist you during the practicum, these cannot substitute for it, as you will need to demonstrate your new learning from the first three courses during the practicum.