I think your question needs some clarifying. If you are asking how to make a glass gaurdrail system to attach to a stair which has a steel middle stringer with cantilevered treads, you will need to hire someone to design a system for attaching the panels to either the treads or stringer.

This space looks like a perfect spot for wallpaper or an accent color...wallpaper is making a big comeback and comes as simple as grass paper to more ornate or modern patterns...also a good option a subtle graphic paint treatment...the simple lines of the bannister invite a vertical stripe or pinstripe paint trtmt also

you are thinking about the space right now. it looks odd, no doubt. 1) when you fill in with the furniture, just make sure the three steps are hidden. 2) consider three potted plants of different height, so the rectangle is complete. 3) glass bowl with Siamese fighting fish for each step 4) figurines of different heights 5) 2inch square wooden bar on each step up to the top of the rectangle. and complete the entire rectangle if you want with a smaller rectangle open in the center my suggestion is, there is a reason why this space ended up like this. it will look great once you put something there. things like these are what make your house unique.

Repaint understairs in white, the wallpaper doesnot work well and have your workstation under stairs