I know that there is a tutorial for this, but I couldn't understand it. the tutorials that I have seen say that you have to open both in paint, or some program, but I don't understand or know how to do that.
Go to "MatrialBase" then to "Tilesets"
Click export on the one's you woud like.
Now open all of them in paint (seperate files)
In pait clck "Image" then "Atributes" now write down all the Heights of the three tilesets, then add them.
Now in one of the tilesets open in paint change the height to the total numder. Now copy and paste the other tilesets under that one making one large tileset.
An easy way is to just export both of the tilesets you want to combine and then delete whatever you want out, and then put it all in by grid. Very easy with photoshop.
That worked, but in the room that had the grassland tile set( I used grassland and castle city), around the trees. the green shows.
1) I don't get it...did you want grass around the trees?
2) And maybe when you edited them, you over lapped them a little bit and maybe that's why the green shows.
I think it's easiest to put all of the city ones into one, that way you're not limited.