Ok here the video
Video
Ok I break it down
In the scene the elf is standing next to a trigger, marked off with the meat placables, the trigger creates a walkmesh placable in another area. This is to test is the walkmesh will load when the pc enter the other area like Failed.Bard said in the other post, I had hoped this worked.
The pc then goes to the other area and walks to the script created walkmesh placables(marked by the visual plant in it corner so we know it was created) and you can see the walkmesh is not loading and the tileset walkmesh is overriding it.
The pc next goes to a placed walkmesh in the toolset and the placable walkmesh is working fine.
The pc then goes to a second trigger this trigger destroys the placable walkmeshes of level 1 deepness, you will notice that the walkmesh that was placed in the toolset does not delete, because the pc has to leave the area for the walkmesh placable that was placed in the toolset to be updated.
The pc leaves the area and comes back and you see that it has updated the deletion of the placable, there is a second placable walkmesh at the same spot that is deeper and you see the pc walking into that.
So if I wanted a sinking effect, I would have to delete the upper level, transfer the pc out of area and back in again delete next level and repeat. (very little immerson for the pc) have all three placeable walk meshes at the same area and placed with the toolset and not scripted in.
I think I just have the one level of depth and use script to stick them(maybe spasm animation on them) and have them use custom feats to get out and/or use rope items that can be used on them from other pcs to get them out and if they fail, knock them down so they look like they went under or jump them to quicksand area.