[Tyhm]

I think the problem is map caching. If you save a level, it seems to save the levels connected to it based on what they looked like when you loaded them. If you edit level13.graal, then edit level14.graal and close it, then finish editing level13.graal and play it, it overwrites the newer level14.graal with its cached version.
Solution: reload the levels on tab-in, save on tab-out? That way if I add a tree to the edge of level13, then click on the level14 tab, voila, the tree is there. I add a bush around the tree, click back to the level13 tab, there's the bush just past the level edge.