How can i make a window cut more than one wall

[KyeyuneEliNathan]

I saw this technique in an Eric Bobrow tutorial where the cutting box of a window can be shown, 

Hence it can be extended to cut a wall next to the wall the window is drawn on

[SenecaDesignLLC]

Draw how it's built.

[Lee Hankins]

I’m not sure that is actually possible. I’ve never seen it done. What you can do is use the opening tool and create a secondary opening where the window is and it will cut through everything it passes through whether that be walls or slabs  

[Bricklyne Clarence]

Copy the window (or window properties using the syringe), place it on the second wall, and change its settings to 'Opening only' so that it's only a hole and opening with the same dimensions as the original window, and then move that opening  to coincide with there the window in the original wall is.

Just be sure if you're creating a window schedule to have it ignore empty openings otherwise it will count it as a second window in the same location.

Windows can't cut walls that are not hosting them.

The opening tool solution also works, but it gives you an extra element to have to work with and creates somewhat of a mess on your floor plan that you have to clean up/work-around..