Need 1st person to 3rd person viewport cam set first.
Simple change 1st person to 3rd view:
In 3rd person viewport
rename follow camera to 3rd person, add new camera child under mesh as 1st person cam
Change socket to head, rotate and move the camera,
tick Use pawn control rotation
untick auto activate (let 1st person view not as a start)
Add switch cam input key in action mapping in Project setting
In event graph: