My particular objection to filling in the space over one opening and not the other is that again it Emphasizes the Difference between the openings that is not particularly emphasized by just putting the treatment on the opening at the opening height. If you are balancing out opening heights the treatments have to be hung at such a level that both can get the same treatment and the discrepancy is actually compensated for visually, which usually means the compensating blind or whatever the treatment is has to be tall enough that a difference between the two is less noticeable. If you didn't Tell me that these windows were at two different heights I don't know that I would pay attention to it: they aren't on the same wall, on the same plane or even in the same part of the room. Having a treatment higher over one window visually than over the door visually (from the frame UP) is only going to point this out. Likewise, I don't think a blind that comes down from the top is a particularly "natural" or functional treatment for a sliding door. A blind can be pulled down over a window to provide shade, and the window can still operate and let in some light. A blind over a slider must be pulled up almost fully off the door for the door to be used. A blind halfway down over a door makes it a non functional door. It's not a treatment that makes much sense on a door since it must essentially be "removed" from the thing it is covering for the thing it is covering to function.

There is another wqy to add sheers behind your drapes and much less expensive than the 'Add a Rod' idea as well as less cumbersome than the bungee idea, depending on the type of rod you use for the drapes. IF you use a standard type curtain rod, there is a solid 'u' shaped hook you can insert into the bottom fold of the of the rod while inserting a regular cafe type rod into it to hold the sheers. They can be found at big box stores and often at drapery stores. lollll But I can't find it on the Internet drapery ads. Mucho inexpensive, mucho easy, and your sheers will definitely be behind your drapes as far as you want.

I would either hang some shades inside the windows or put the rod above the top window trim and wider than the side trims. Those windows & window trim look really nice so why not allow them to be seen. I'd personally go shades inside the window frames. You get privacy, block that view of siding and old fence, and still get to see those nice looking trimmed windows.

Hard to say without a picture.