This gives the designer a very detailed idea of what to do in desgning a beamsplitter.

Excellent article. This was really helpfull to me.

Few little suggestions for improvement:
For a beginner like myself, I think page 5 (example part D) was a bit difficult. This was the first time I worked with the Multi-Configuration editor, and you don't really explain what you're doing there.

Maybe you could include a few word about the MCE, and how you will be using it for the beamsplitter, before we start to put data into it?
Also please explain in a few words what the PRAM operand does. (Took me a long time to find it in the help files...)

What also confused me for a while, was that I didn't see the rays coming back from the mirror (surface 7) Took me a long while to discover that the 3D Layout Settings kept the surface at #7 (image in config 1). I think that happens always. (at least in my version.) Maybe add a little remark that if you don't see those rays, you need to check the layout settings for the last surface?