Cut landscape mesh with blueprint (Like a dynamic boolean operation)

So this guys does it: https://youtu.be/1U-5zxJCIN4?si=gCg7ARfqOEWSOw09&t=157
But I still cant recreate the same result yet

https://www.reddit.com/r/UnrealEngine5/comments/1d5j7gc/how_can_i_achieve_this_same_effect_set_visibility/