We are building our house now, and after installing floor to ceiling windows on the first floor, we noticed that moisture was "pulling" through the masonry barrier inside the house through all 3 windows. The windows on the first floor were installed on the masonry barrier, but that is not the case on the top floor. Here, the windows are mounted on the floor slab.
On the first floor, the windows from floor to ceiling were sealed from the inside with sealing tape. Such sealing tape had not yet been applied to the exterior. (But it had already been applied to all the other "normal" windows).
Of course, I will discuss the situation with the window installers, but I would like to be prepared for the conversation.
The area you show must have at least one black coat or bituminous adhesive membrane.
On the first floor it is overlaid with a window sill. But this is not possible on a patio if the height is to be FFB.
Water drains to the wall barrier, under the window and into the room.
The wall barrier must be cut off and the window sealed against water infiltration from the outside.
What strikes me about your picture: what is the material that serves as the floor structure? There are some very thick stones there. It's not gravel or RCL. There's some kind of dirt poured in there. All in all it looks very questionable.
Okay, then the procedure would be: Apply the patio slab to the window and seal it with silicone. But silicone on the window and moisture barrier wouldn't hurt either. Then the moisture won't get in.
In our case, the floor-to-ceiling windows were sealed from the outside with liquid plastic and fleece. This waterproofing was applied to the bitumen thick coating of the basement wall and then the insulation was applied over it. The same applies to the front door and garage door.