The Servicemember Civilian Transition Support Act requires the Department of Defense to designate a senior official within 90 days to oversee all military-to-civilian and military-to-reserve transition programs and policies. This official, selected from candidates with extensive veterans services experience and knowledge of military transitions, will serve as the principal advisor to the Secretary of Defense and act as the chief transition officer for the entire department. The designated official's responsibilities include reviewing existing transition programs like the Transition Assistance Program and Skillbridge, coordinating with the Veterans Affairs, Labor, and Education departments to improve service delivery, and proposing improvements to ensure all service members are prepared for civilian life or reserve status. The Secretary of Defense must brief Congress within 90 days on the status of this designation and how the new official's roles and authorities will be implemented. This legislation essentially centralizes military transition services under one senior official to improve coordination and effectiveness across the Department of Defense.