As far as I konw you cant change the geometry of static meshes in unreal, like making holes in them or so. you only can change their x/y/z dimensions to deform them. guess thats why they are called “static” meshes.
Also for youre door idea you would have to modify the collision boxes of the walls and make a hole in them for the door.
suggestion instead of this: why not have one optional door wall module that can connect 2 door modules and make them walkable?