@Melkino: At the moment the horizontal stairs are passable, the character walks straight across it, and as you say that looks awkward. But to fix this I had to "event" the character's movement up the stairs, when they approach them.
Set Move Route: Player :$>Move Upper Right :$>Move Upper Right :$>Move Upper Right
walks diagonally up the stairs. (right stairs) Not ideal but looks better.
Another way would be to use a 8 directional movement script, so you don't have to event anything.