Manually operated roller shutters - space above the window

Our manually operated built-in roller shutters above the windows are exactly 20cm ...

Ours are also at least 20cm.
Here is a picture:

At the moment there is no roller shutter box at all. The roller shutters are simply mounted on the outside above the windows on the facade. I believe that's called retrofit roller shutters.

That’s correct as to the name. However, they are not "simply" mounted: normally yes, but apparently not here. Normally at a height where there is still a lintel above the window, but in your case there is already the ceiling. So the strap or crank feed would have to be far down on the box for you, and then extended and redirected through a hole in the wall. That is at least not trivial, but absolutely impossible if the box is not designed near the lower end. I could imagine that one wants or has to use a model here which, due to radio control and therefore inevitably electric operation, allows no alternative at all. Hence my question about the sketch of the thing.

I just press one button and move on

But you don’t always want the shutters completely closed. But I admit: it is certainly convenient in a positive way. Nevertheless, I think the same as : I like to walk through the house and lower them manually. They are then also in the place I want them within a second. More or less;)

Oh damn. If 11ant as a window expert already says that it’s not that "simple," then it will probably have to be electric. Well, worse things happen. But still annoying. A planning mistake, I think.

Or you take shutters with adjustable slats. They are manual and adjustable in light transmission.

Hampshire, that might also be a good idea! I'll take a look around right away to see how they work. I don't have a manor house, but I can turn my shoebox (aka terraced house) into a manor house. :D