Laying large stones like tiles?

then you need the opposite of level The grates should not stand higher than the covering, rather about 1mm lower. If you want to notch this at the edge now, you won’t get the transition permanently sealed

Does anyone have "pro" or "con" reasons for this?

The first thing I think of is that you want to create a kind of tub, so you want to tile the area of the black tiles about 2-3 cm higher than the rest… then the water can no longer flow off over the edge. Ok, it's not supposed to, because then the edge would get damaged over time. Even if you have a drain, water might still remain. Ps. I only just saw the responses… and I don't understand it. So forget my contribution if it's not needed.

Hello
To answer your question precisely: Yes, it works exactly as you intend.
The balcony surface has already endured several summers as well as winters, including watering.
That means: the waterproofing layer underneath has worked so far.
Why shouldn't it continue to work? (rhetorical question)
The slope should be checked as a precaution to ensure that no puddles actually remain in front of the door entrance (as previously speculated).
The "critical point" remains the wall connection to the new surface covering.
To prevent driving rain from getting in through the edge joint, a (new) drip edge should be installed at the base.
However, the old tile surface should first be diamond ground, vacuumed, and cleaned thoroughly with an alkaline basic cleaner (then neutralized with clear water).
Primer with 2K reactive resin, sprinkled with quartz sand 07/1.2, so that the adhesion between the old tile surface and the new structure does not fail later.
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Regards: KlaRa

this is what the situation will look like:

The concrete slab is about 14 cm thick and I don’t want to cut into it (to get the rebate).
The whole thing is still in planning and I was interested to know if there are reasons against gluing 2cm thick granite slabs.
It makes sense to me that tiles and frost are not compatible in the long run.

Meanwhile, I am reconsidering sticking with wood instead of granite slabs (which were supposed to be laid on the new balcony). In that case, I would cover the old balcony - after removing the tiles - with a thinner layer of concrete (the stuff is called "Plan B", so it fits my situation ;))

Because it is still open which materials will be used, a discussion about that is too confusing.

I thank you for the hints and comments. :)

The granite slabs would add considerable weight to the balcony.. can it even hold that??