As you can drag over multiple bodies at once you could store an array of the current hovered bodies, and on drop iterate over them / find the closest one etc.
var bodies_over := []
func _on_area_2d_body_entered(body:StaticBody2D):
if body.is_in_group('droppable'):
bodies_over.push_back(body)
...
func _on_area_2d_body_exited(body):
if body in bodies_over:
bodies_over.erase(body)
...