Record button is there to record already existing animations.
You can create one “dead” pose animation for your body, manually edit this animation within unreal engine and duplicate several 1 frame animations with different poses. Editing Animation Layers | Unreal Engine 5.1 Documentation
Than play random animation with blueprint on body spawn.
Another way would be physical simulation like here: watch?v=T_gvrQjsAoQ
Than you need to place your bodies on the map and they will fall randomly or record animation directly from physic asset simulation preview.