Floor plan design single-family house with around 150 m²

yes, unfortunately that's true. Sometimes even 30-40 cm are enough to visually connect the sofa with a floor-to-ceiling window.

That's how it is. But in a 4 x 4 living room, that's 40 cm along the entire length or even the whole width of the house.

hard to clean, doesn't really make it bright, can't be opened

But it doesn't have to be with an additional window, like Chris's.

The standard sill height came about because we A) at the time thought it was stupid to see the back of the sofa from the garden and B) wanted a place to put flowers etc. on the window.

We've discussed your side window quite often, and I think you're very brave in how honestly you deal with it. Others sugarcoat their "mistakes" and get annoyed outside the forum.
We also have a side window: 2 meters wide and floor-to-ceiling. At the time I chose the 40 cm sill for possible flowerpots (See ), because I like the '50s style.. The seller immediately advised us to be more generous, a clear line of sight into the garden without any barrier, etc., and luckily we realized it that way.
I'm still not the type to put flowerpots on window sills ;) – instead there's an armchair in front of one half now :p. … with enough space (our room is about 5 x 5.5), so my vacuum cleaner fits between. Naturally, more light comes through this window element than just a window with a sill. It has since become my husband's favorite spot, and also mine when I knit. Because of the amount of light. You can walk through the element next to it.
And if the armchair ever moves elsewhere, maybe a nice side table will be placed there. Or a palm. Or nothing at all, with a clear view of the lawn or the tree behind it. We have a full view of the maple, and that's just beautiful.

I also think it's really good that you openly admit to the "mistakes." Nevertheless, I still believe Instagram is only about appearances.

and many are also just visualizations, e.g. home by me. I also noticed that many of these "design artists" come from Russia.

Example

[ATTACH alt="Screenshot 2021-10-13 at 18-32-18 Home inspirations trends and decorating ideas HomeByMe.png" type="full"]66093[/ATTACH]

I also think it's very good that you openly acknowledge the "mistakes."
Nevertheless, I remain of the opinion that Instagram is all about appearances.

Yes, sure, of course a lot is just about appearances. But sometimes it also has added value, like, for example, a somewhat less obstructed view outside, which is reduced by another 20-30cm above the sofa backrest due to the parapet.

To illustrate it, something like this would be great (plus another window on the other sofa back side).
From the wall side, you can have a great view outside over the sofa backrest, and with the estimated 30cm setback here, it doesn't look cramped at the window.

I like to look out the window from the sofa. I don't have anything in front of it at all. To me, it often feels like, oops, there still need to be some pieces of furniture. Below, the sofa stands in front of the window, above the cable mess from the desk, etc.

I like to look out the window from the sofa. I don’t have anything in front of it at all. For me, it often feels like, oops, there still need to be some furniture.
Below the sofa is in front of the window, above is the cable mess from the desk, etc.

Yes, that would of course be perfect if you can manage it that way, with all the other interests that also need to be considered:
Direct view to the TV, to the books/HiFi shelf, to the fireplace, the sofa should not have its back to the dining table, it should be a corner sofa, ... doing all this with actually only a few available walls and limited space is really not easy