Hummm, I guess this is hardcode so there's no possibility to do it without tricking a little bit with scripting. Even I think you should have to implement your own pathfinding algorithm in WME...
As far as I know WME implements some kind of A* algorithm for pathfinding because in 2D adventures the goal is to reach certain point following the optimal path and going up and then left as you've suggested is not a very optimal aproach for this.
If you want to look further on this topic there's an example of Dijkstra algorithm implementation in WME by "metamorphium" -->
http://forum.dead-code.org/index.php?topic=723.0