Install a window afterwards?

Possibly plan for a roller blind. A kitchen countertop that extends into the window also looks quite nice. You probably want the sink under the window? Then definitely pay attention to the possible collision with the faucet. If no tilt/turn function is needed, fixed glazing is much cheaper.

we are currently dealing with the kitchen renovation. It is planned to replace the existing kitchen in about 2 years and also change the layout. We also want more daylight and a nice view of the front yard and garden. Our wish would therefore be an additional window above the kitchen row, specifically above the sink.

Almost no one sees the new window, certainly not from the street, so it should actually not concern anyone.

Then just do it. The location and what you say should not be of interest for an external effect.
Before carrying it out, I would initiate a kitchen discussion, here or in another forum, that deals specifically with kitchens. Then both can be implemented homogeneously together.

Possibly consider planning for a roller blind. A kitchen countertop that extends into the window also looks quite nice. You probably want the sink under the window? Then definitely pay attention to the possible collision with the faucet. If no tilt/turn function is needed, fixed glazing is much cheaper.

In this configuration, I would consider choosing a window where only the lower third is fixed glazing, and above that, two sashes. That often provides the crucial centimeters for the faucet and you have the advantage that you don't always have to clear everything away when you want to open the window.

Be sure to choose the window height so that the countertop runs up to the window – we have that currently, and it is really super practical!

So I also don’t think you need the building authority for a window, but I would contact them in advance and ask, that’s better. Otherwise just get the mason for the lintel. I almost think the mason does the statics himself, right? Yes, and then plaster again. You don’t have any additional insulation, just the Ytong?
I would roughly estimate the window at €800, of course it can also be significantly more. The window can be installed by yourself. No idea what the craftsman charges for that. Inside, the connection to the plaster has to be restored again. I would throw around €2500-3000 in my imagination. A lot of money and dirt for a bit more light.

According to the scope of work description, it should only be Ytong with plaster, yes.
Inside we would have to redo the wall anyway because the old tile backsplash has to come down, so I would plan that in.

Our house unfortunately has hardly any windows on the south side, and that is really a shame. "A bit more light" would in this case change the whole room atmosphere.
Currently, the short side of the L-shaped kitchen is partly under the only window, and under the rest of the window is the dining area. But that is totally cramped. Therefore, the dining area should get more space there. Then the kitchen L would be completely without a window – I would find that really a shame. If it is possible somehow, that would be more important to me than other "frills" on the kitchen. :)

Maybe plan a roller blind. A kitchen countertop that extends into the window also looks quite nice. You surely want the sink under the window? Then definitely watch out for the possible collision with the faucet. If no tilt-and-turn is needed, fixed glazing is much cheaper.

True, we have roller shutters everywhere, so that should be included there as well. I would also find integrating the countertop very nice.
Actually, the window would only be possible exactly where water/sewage lines are, and I don’t want to have those moved. We don’t have a basement underneath, that would be a huge mess, and I don’t want to touch the floor either. I was thinking of a solution with a fixed lower element.

Then just do it. The location and what you say shouldn’t be interesting for outside appearance.
I would suggest starting a kitchen discussion before implementation, here or in another forum, which deals specifically with kitchens. Then you can implement both things homogeneously.

I will definitely do that. :)

In this constellation, I would consider choosing a window where only the lower third is fixed glazed, and above that two sashes. That often gains the crucial centimeters for the faucet and you have the advantage that you don’t always have to clear everything away if you want to open the window.

Definitely choose the window height so that the countertop runs through up to the window – we currently have that and it is really super practical!

Yes, that’s roughly how I imagined it too.

Also think about the splashes. I really like our window right by the sink. But the lower window constantly gets splashed. Next time I would tend to build higher here, tile, and then have the window directly without the lower part. It doesn’t look as good visually (which is why we decided against it back then), but it’s probably more practical.

Thank you, good point, I need to think about that again...