Your photo is fairly dark, and it's hard to see how this space relates to those around it. Can you post some additional photos?

I'm having trouble piecing together what you're saying. Before you can "fill the space", you need to define the space. What is that room? What will it be used for? I can't tell you how to decorate it when I don't know what it is. Is it a breakfast nook? An office off the kitchen? A reading/sun room? And then in terms of you don't want anything to cover the windows but you need privacy .... if you need privacy, you're going to have to cover them with something, right. I can't really tell, but maybe you could get away with blinds on the windows and leave the sliding door bare. It doesn't look like there's room for anything more anyway.

From which side can the neighbor see into the space? Is the deck “yours”?

Could you provide a photo with an alternate view? That would be helpful to see how much space you have.... If you don't want to have drapes or blinds, you might consider solar shades. They give a sense of privacy & filter the sun, but won't have the bulk of other treatments. You can choose the level of light filtration as well.

If you like having chairs in that space, consider replacing the acrylic with something that has more visual weight... Good Luck!