Change wall cutout for resized window without blender

Hey everyone!

So I haven't been modding for months and as I checked up on Sims 4 Studio, I have noticed that the resize tutorial has gone.

I have ZERO experience with Blender and did my last resize with Sims 4 Studio on its own.

How do I change the cutout without blender? Which mesh do I have to choose? I enlarged a window, but now the hole is still the same size.

Thanks in advance.