@ Holly.
This shows the layout in front of the block. On the far left is MM's window with the front door out of sight beyond it. The small and larger windows belong to 5B, where the Oldfields stayed. Their front door can be seen inside the entrance on the left. Inside there were also the stairs and lift to the upper floors, the door to 5C (unoccupied) and to 5D where the O'Brien/Tanner couple stayed.
The slope and steps were in front of the main entrance to the right of the picture.
That's a good photo. I haven't seen that one before.
I have a wealth of information in my head about this Topic, but I don't know how much of it is true. But people crossing the car park don't appear to have had 5a in their sight without directly looking, which wouldn't have helped much as 5a was in deep shadow.
The McCanns did not take a buggy with them, although they appear to have hired one after Madeleine disappeared.
No one seems to know if Madeleine's bedroom window was locked, so it could have been unlocked. And it was possible to raise the shutters from outside, as shown by PeterMac.
It was also possible to climb in the window because there is a video of someone from The PJ doing just this.
Personally, I think the abductor crept down low up the back patio steps, but could not have done this carrying a child, and closing the patio door and both gates as well.
As for the abductor sedating all of the children, then Google "Making Chloroform", anyone can do it.