It look to me you do have enough space. Place one of your dining chairs under the window, and leave it there for couple days, and see how do you feel about it. Or just a tiny bench.

Pretty space! I think I'd hang art there and leave it open. But Lila's advice is good about placing a chair there temporarily to see how traffic flows. You could add a large rug under your dining table for more pattern and texture if you feel like something's missing.

I appreciate those renderings!

I moved an antique pie safe there (normally lives at other end of table) and I liked having something there but it was too deep for that spot.

I second the dining room rug, husband is pushing back on that saying I already have too many (lol) and it’s easier to clean under it without one.

Curtain panels matching the ones on the slider.

Second @ShadyWillowFarm's suggestion of continuing on with rods and draperies for all the windows. Hang rods at the same height.

I like the side table with plant/ greenery greenery suggestion. I like the style here, much taller smaller table of course. I wouldn’t include seating.

Thank you for suggestions!

I would not put anything on the floor (furniture) but would stack some art in that space