I think one of the long tables need go go first, maybe the one against the left wall. Then you could move your armchair to the upper left corner near the window with the ottoman. Maybe you can put a small side table next to the armchair for your coffee and books?

Remove both sideboard. Too big for space. Get a desk, pier one has one. Glass top about 5 ft long and 30" wide would fit by window. With nice chair. Angle in corner where plant is pull drapes back to other side, there are hooks you can buy to keep drapes pulled back. That will bring light in and open up space. Add plant to that side too. Keep big chair add a small table next to it. Add floor lamp behind desk. Ikea has some. In Stainless. A brighter rug or a crow hide, also Ikea would add interest. Angle like desk.

Add box to side of chair not in front. Use as a table. Get a small foot stool in Zebra. Remove all small items. No clutter.

Setting up a home office in that space is a perfect idea. I would suggest an L-shaped desk that runs along the left wall and under the window and relocate the sideboard currently on the left wall to behind the sofa for storage. Slide the armchair up the left wall, closer to the desk area. Depending on your at-home work needs, you could add vertical storage on the left wall with shelving. Beautiful space! I think I have the same buffet as the one on the left :)

Have added a second photo for clarity.

I would replace with a desk as sofa table - long and narrow but that you can put your feet under - upholster one of those executive rolling chairs with a great modern graphic neutral that will contribute to your space. Move the lamp to this off the sideboard, then put a new eames or your existing leather chair and add an ottoman at the window so you have a place to be comfortable using the laptop. The desk/sofa table sideboard is just a good place to leave it closed down when you are out / place to do paperwork as the need arises. Keep the sideboard on the back wall, but shift it away from the window / trade it with the armchair I see. Having a desk to sit at is surprisingly useful in a living space.

You have too much on walls and area. Replace art pieces with very tall big vertical mirror.

Building on Travis idea, put desk in corner facing room diagonally, ghost chair, industrial stainless desk lamp, you might want a tall narrow bookshelf between leather chair and desk on left wall instead of a mirror, directional floor lamp behind leather chair. No zebra - go with black modern leather/ chrome footstool with the hide.

I love your sideboards - send them to me!

And yes - great spot for a desk. :)

I agree with HERE - also I like your artwork on the walls and it goes with the style you have created in the parts of your home we can see.

love the art work.. many good ideas above for the office bit...
just adding my two bit to that.. i wish you can keep the room looking the way it is.. but add storage for your office work below the desk level.. not above it.. i-e nothing offie related on the walls.. that is what i feel would keep it looking like part of your living room too.. i-e so that office doesn't 'take over' the look of the living room. which is quite nice!

Where did you get your rug? Love it!