I don't think you'll be able to mount a rod above the triangle window. It's not going to work out like the rendering. Instead, it'll hit the ceiling on the left. I think hanging the curtains right under the ceiling, makes the smaller windows look unbalanced because of the transom on only one window.
I think you're better off with just shades or blinds in this situation.
You could have shaped curtains made, then hung on knobs over the triangle window, and then hang curtains further down over the smaller windows.
Q