Hi, thanks for the question. I think an easier might be to use two L1S generators, one nested inside the other.
To do this I've sliced the window into 3 part, a bottom and top that don't change and a mid section that will be scaled.
Using these you can create a RC object using a single spline, as follow:
1 - Add the bottom segment to the Start, the top to the End.
2 - Create a compose operator and add the top, a null segment, and then the bottom.
3 - Wire this to the Corner input.
4- Finally add the mid segment to the Default input and set the mode to Scale
5 - You can now draw a spline for the total height of the building. Every time you add a new Vertex you set the height of a window. This will give you one vertical strip like this...
You can now add this to a second RailClone object that also uses an L1S array. Create a spline for the path of your façade, create a segment picking the window RC object. Wire this to the the Default
input. In the attached example I've also added the corner segment as a second generator. This is because you can't slice corners in Adaptive mode so I'm using one generator for the windows in adaptive mode, and a second generator in tile mode to add the corners.
Attached is a sample file to demonstrate this technique.
I hope that helps, please let me know if you have any further questions.