The textures already blend. I'm not sure what you mean about the built-in editor, either.
If you mean canceling out the blur so that it looks good on tiles (The kind of flooring, not a square texture ), you can take a screenshot of the game with the two tiles in question fully visible, cut them out, save them under new names, and apply them where the old ones were. The blur will completely cancel itself out and you will end up with sharp edges. The reason you have to do it this way is because you can't actually turn the blending off at all, let alone on a per-tile basis.