Terrace level with the ground? Or with a step?

Continuously adjustable with slope
No waterlogging may occur in the area

We also paved it with a continuous slope towards the garden. We do not have a channel in front of it. Our landscape gardener said that with sufficient slope and roof overhang, it is not necessarily needed if the connection is properly sealed. For us, this was done with EPDM and suitable adhesive. In front of the paving there is also a drainage sheet. By now, we have a 4-meter deep terrace roof above it, so water never gets there... A threshold-free patio door would be even better, but more complex and expensive. So basically wheelchair accessible....

I initially decided internally on a ( uglier ) stepped solution.

Why "initially"? - to me, it looks as if you have actually implemented the threshold solution structurally. I would treat it analogously to a shower tray, i.e. for safety, bring the terrace to the same level as the room floor. You are making the step over the high threshold anyway, and then your take-off and landing heights are identical.

For someone who has fussed over every little detail for so long, I would have expected this "level" solution - but with a flat threshold and a channel! - just considering how long you have thought about slimmer frames.

I would then ramp the lawn area.

It seems to me that with the solution: floor height inside = terrace height the ventilation slots in the clinker are then exactly at terrace level. Not so cool.

Alternative solution: wooden terrace at floor level, boards sloping away from the house. No water accumulates at the window - but it's a matter of taste and somehow you rarely see that here.

We have a special sealing slurry on the facade in the area of the terrace access. The wooden terrace is at the same level as the floor inside. We have a barrier-free threshold. Directly under the wood, adjacent to the facade/sealing, a channel is installed. None of this can be seen through the wood. The wood only needs 2-3 cm of clearance because it expands...

With us: stepless access to the terrace with a low threshold, channel connected to drainage, terrace with slope.