Are you looking to have a TV in the space? If so, can you post images of the other walls? You might be able to do a similar layout to this design of ours below, and if you're trying to do a TV there might be a better layout.

Mt. Washington Ski House · More Info

Mt. Washington Ski House · More Info

Use graph paper and a ruler to layout your space in scale. Next, in the same scale draw and cut out your desk and chair, your sofa and any alternative pieces you want to consider. You can move the cutouts around your scale layout to explore different placements. IKEA has good storage options. Also Facebook Marketplace and Habitat could be sources. I like the Uppland sectional because it has pocketed springs in the seat cushions and removable coverings to wash or change the look.

I have lived in a lot of small spaces. I'm not a fan of bookcases or other storage units to divide up a space. I think they are bulky in small spaces, and actually make a space feel smaller and cut up. I'd instead find some visual cues to make the office nook feel like a different space.

Use a rug that just fits into the office space and another one in the living space.

Hang a narrow curtain panel perpendicular to the wall where the anatomy poster is. It isn't to hide the office space but just to create a psychological delineation.

If you want some greenery, they make fantastically realistic looking fake plants these days. You could get a tall floor plant and place it where the anatomy poster is and that too would divide the spaces.