Second small sink on kitchen island

This will be quite a large kitchen. You would have enough space on the island for a sink.

The kitchen is designed so that you work with your back to the room and looking outside. That's where I see most of the workspace. A sink is practical where you need it and don't have to "walk over" to it first. Usually, that is at the cutting area or where dirty items like knives and boards accumulate that don't belong in the dishwasher.

Personally, I wouldn't add a second sink in your setup. Although the kitchen is spacious, with quite a large aisle space, you are still close to the sink quickly. A sink always needs to be kept clean, and you need towels at both sinks. But the space allows it; you can’t go wrong.

You didn't ask, but I'll give you a tip anyway: think carefully about where you want to work mainly: at the island or rather at the counter? The cooktop "cuts up" the nice workspace on the island. 80 cm on each side is okay, but really just okay, and would be too little for me. Especially if the cooktop can be moved easily. Because of downdraft, the cabinet layout would probably change, but I'd prefer that over a cooktop in the center.

If you prefer to work facing the room, I would probably plan the sink on the island and the cooktop on the counter. You need water more often than you actually stand at the stove. And regardless of where the sink will finally be: with so much space in the kitchen, I would definitely choose a larger sink.
If the (main) sink were on the island, opposite it could even be a tall cabinet with a built-in dishwasher. I had that setup once, and it was great.

The kitchen was one of the most important parts of the house, we are five people and until now we always had a small U-shaped kitchen where you constantly step on each other's feet.
Thank you very much for your suggestions!
I actually find the 80 centimeters to the left of the cooking area sufficient; I have never had that much space available, and for pizza and cookies, I thought it would also be possible to work from all sides.
And then there is also the terrace door, so I found the middle to be quite good for the cooktop.
I actually want the sink by the window, then I can cook together with the children at the island.
But moving the cooktop a bit closer to the wall probably wouldn’t be a bad idea.

The kitchen itself is consistent for me,

I probably won't need it in that sense, it would just perhaps be a nice to have...

Well, that's a bit of a catch-22: you actually don't need a second one. If you had one on the island, you wouldn't use the one at the window because at a distance of 150 it's quite far away. But: if the sink is on the island in addition to the stove, there's hardly any workspace left on the island and it pushes you to the line by the window, which then again makes the sink on the island unnecessary.

Yes, well, seen like that you are right again

A second smaller sink can be practical for espresso fans near the portafilter machine. But you can be just as happy with only one sink :-)

If you prefer to work towards the room, I would probably plan the sink on the island and the cooktop on the line. You need water more often than you actually stand at the stove.

You constantly read this "mantra" from the other forum, at least there. And I can't explain at all where it comes from. For me / for us it is not the case at all. We stand significantly (!) longer at the stove than at the sink. You just rinse something off quickly and that's it. I stand at the stove during the entire cooking process. I would leave the kitchen as planned.